diff --git a/rtengine/bilateral2.h b/rtengine/bilateral2.h
index 0c59f9db5..0a7cb7bb8 100644
--- a/rtengine/bilateral2.h
+++ b/rtengine/bilateral2.h
@@ -26,7 +26,9 @@
 #include <mytime.h>
 #include <gauss.h>
 #include <glibmm.h>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 // This seems ugly, but way faster than any other solutions I tried
 
diff --git a/rtengine/gauss.h b/rtengine/gauss.h
index c9e25a0b0..527274b02 100644
--- a/rtengine/gauss.h
+++ b/rtengine/gauss.h
@@ -23,7 +23,9 @@
 #include <string.h> 
 #include <math.h>
 #include <alignedbuffer.h>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 // classical filtering if the support window is small:
 
@@ -31,7 +33,11 @@ template<class T> void gaussHorizontal3 (T** src, T** dst, T* buffer, int W, int
 
 	#pragma omp parallel for if (multiThread)
     for (int i=0; i<H; i++) {
+#ifdef _OPENMP
     	T* temp = buffer + omp_get_thread_num() * W;
+#else
+    	T* temp = buffer;
+#endif
         for (int j=1; j<W-1; j++)
             temp[j] = (T)(c1 * (src[i][j-1] + src[i][j+1]) + c0 * src[i][j]);
         dst[i][0] = src[i][0];
@@ -44,7 +50,11 @@ template<class T> void gaussVertical3 (T** src, T** dst, T* buffer, int W, int H
     
 	#pragma omp parallel for if (multiThread)
     for (int i=0; i<W; i++) {
+#ifdef _OPENMP
     	T* temp = buffer + omp_get_thread_num() * H;
+#else
+    	T* temp = buffer;
+#endif
         for (int j = 1; j<H-1; j++) 
         	temp[j] = (T)(c1 * (src[j-1][i] + src[j+1][i]) + c0 * src[j][i]);
         dst[0][i] = src[0][i];
@@ -107,9 +117,11 @@ template<class T> void gaussHorizontal (T** src, T** dst, AlignedBuffer<double>*
     
 	#pragma omp parallel for if (multiThread)
     for (int i=0; i<H; i++) {
-
+#ifdef _OPENMP
         double* temp2 = buffer->data + omp_get_thread_num() * W;
-
+#else
+        double* temp2 = buffer->data;
+#endif
         temp2[0] = B * src[i][0] + b1*src[i][0] + b2*src[i][0] + b3*src[i][0];
         temp2[1] = B * src[i][1] + b1*temp2[0]  + b2*src[i][0] + b3*src[i][0];
         temp2[2] = B * src[i][2] + b1*temp2[1]  + b2*temp2[0]  + b3*src[i][0];
@@ -183,9 +195,11 @@ template<class T> void gaussVertical (T** src, T** dst, AlignedBuffer<double>* b
 
 	#pragma omp parallel for if (multiThread)
     for (int i=0; i<W; i++) {
-
+#ifdef _OPENMP
         double* temp2 = buffer->data + omp_get_thread_num() * H;
-
+#else
+        double* temp2 = buffer->data;
+#endif
     	temp2[0] = B * src[0][i] + b1*src[0][i] + b2*src[0][i] + b3*src[0][i];
         temp2[1] = B * src[1][i] + b1*temp2[0]  + b2*src[0][i] + b3*src[0][i];
         temp2[2] = B * src[2][i] + b1*temp2[1]  + b2*temp2[0]  + b3*src[0][i];
diff --git a/rtengine/improcfun.cc b/rtengine/improcfun.cc
index afa99d020..d8ed0d8f0 100644
--- a/rtengine/improcfun.cc
+++ b/rtengine/improcfun.cc
@@ -27,7 +27,9 @@
 #include <mytime.h>
 #include <glibmm.h>
 #include <iccstore.h>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 namespace rtengine {
 
@@ -192,7 +194,13 @@ void ImProcFunctions::firstAnalysis (Image16* original, const ProcParams* params
 	}
 
 	// calculate chroma radius and histogram of the y channel needed for exposure curve calculation
+
+#ifdef _OPENMP
     int T = omp_get_max_threads();
+#else
+    int T = 1;
+#endif
+
 	int* cr = new int [T];
     unsigned int** hist = new unsigned int* [T];
     for (int i=0; i<T; i++) {
@@ -202,6 +210,7 @@ void ImProcFunctions::firstAnalysis (Image16* original, const ProcParams* params
     }
 
     int H = original->height;
+#ifdef _OPENMP
 	#pragma omp parallel if (multiThread)
     {
 		int tid = omp_get_thread_num();
@@ -213,7 +222,9 @@ void ImProcFunctions::firstAnalysis (Image16* original, const ProcParams* params
 		else
 			firstAnalysis_ (original, wprofile, hist[tid], &cr[tid], tid*blk, H);
     }
-
+#else
+    firstAnalysis_ (original, wprofile, hist[0], &cr[0], 0, original->height);
+#endif
     chroma_radius = cr[0];
     for (int i=0; i<T; i++)
     	if (cr[i]>chroma_radius)
@@ -421,9 +432,11 @@ void ImProcFunctions::lumadenoise (LabImage* lab, int** b2) {
 void ImProcFunctions::colordenoise (LabImage* lab, int** b2) {
 
   if (params->colorDenoise.enabled && lab->W>=8 && lab->H>=8) {
-
+#ifdef _OPENMP
 	  AlignedBuffer<double>* buffer = new AlignedBuffer<double> (MAX(lab->W,lab->H)*omp_get_max_threads());
-
+#else
+	  AlignedBuffer<double>* buffer = new AlignedBuffer<double> (MAX(lab->W,lab->H));
+#endif
       gaussHorizontal<short> (lab->a, lab->a, buffer, lab->W, lab->H, params->colorDenoise.amount / 10.0 / scale, multiThread);
       gaussHorizontal<short> (lab->b, lab->b, buffer, lab->W, lab->H, params->colorDenoise.amount / 10.0 / scale, multiThread);
       gaussVertical<short>   (lab->a, lab->a, buffer, lab->W, lab->H, params->colorDenoise.amount / 10.0 / scale, multiThread);
diff --git a/rtengine/iplab2rgb.cc b/rtengine/iplab2rgb.cc
index c7425e434..659d839a2 100644
--- a/rtengine/iplab2rgb.cc
+++ b/rtengine/iplab2rgb.cc
@@ -20,7 +20,9 @@
 #include <improcfun.h>
 #include <glibmm.h>
 #include <iccstore.h>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 namespace rtengine {
 
diff --git a/rtengine/ipresize.cc b/rtengine/ipresize.cc
index c70479f57..c36d34a6b 100644
--- a/rtengine/ipresize.cc
+++ b/rtengine/ipresize.cc
@@ -19,7 +19,9 @@
 #include <rtengine.h>
 #include <improcfun.h>
 #include <glibmm.h>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 namespace rtengine {
 
diff --git a/rtengine/ipsharpen.cc b/rtengine/ipsharpen.cc
index 7cc4ddfaa..98345d98f 100644
--- a/rtengine/ipsharpen.cc
+++ b/rtengine/ipsharpen.cc
@@ -18,7 +18,9 @@
  */
 #include <rtengine.h>
 #include <improcfun.h>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 #include <minmax.h>
 #include <gauss.h>
 #include <bilateral2.h>
@@ -66,9 +68,11 @@ void ImProcFunctions::deconvsharpening (LabImage* lab, unsigned short** b2) {
     }
 
     float** tmp = (float**)b2;
-
+#ifdef _OPENMP
     AlignedBuffer<double>* buffer = new AlignedBuffer<double> (MAX(W,H)*omp_get_max_threads());
-
+#else
+    AlignedBuffer<double>* buffer = new AlignedBuffer<double> (MAX(W,H));
+#endif
     float damping = params->sharpening.deconvdamping / 5.0;
     bool needdamp = params->sharpening.deconvdamping > 0;
     for (int k=0; k<params->sharpening.deconviter; k++) {
@@ -118,9 +122,11 @@ void ImProcFunctions::sharpening (LabImage* lab, unsigned short** b2) {
 
     int W = lab->W, H = lab->H;
     unsigned short** b3;
-
+#ifdef _OPENMP
     AlignedBuffer<double>* buffer = new AlignedBuffer<double> (MAX(W,H)*omp_get_max_threads());
-
+#else
+    AlignedBuffer<double>* buffer = new AlignedBuffer<double> (MAX(W,H));
+#endif
     if (params->sharpening.edgesonly==false) {
 
         gaussHorizontal<unsigned short> (lab->L, b2, buffer, W, H, params->sharpening.radius / scale, multiThread);
diff --git a/rtengine/iptransform.cc b/rtengine/iptransform.cc
index 331f839aa..9a5d977fc 100644
--- a/rtengine/iptransform.cc
+++ b/rtengine/iptransform.cc
@@ -18,7 +18,9 @@
  */
 #include <rtengine.h>
 #include <improcfun.h>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 #include <mytime.h>
 
 namespace rtengine {
diff --git a/rtengine/rawimagesource.cc b/rtengine/rawimagesource.cc
index 0e91184f0..af2c643f8 100644
--- a/rtengine/rawimagesource.cc
+++ b/rtengine/rawimagesource.cc
@@ -25,7 +25,9 @@
 #include <iccstore.h>
 #include <image8.h>
 #include <curves.h>
+#ifdef _OPENMP
 #include <omp.h>
+#endif
 
 namespace rtengine {
 
@@ -962,6 +964,7 @@ void RawImageSource::correction_YIQ_LQ  (Image16* im, int times) {
         return;
 
     for (int t=0; t<times; t++) {
+#ifdef _OPENMP
 	    #pragma omp parallel
     	{
     		int tid = omp_get_thread_num();
@@ -973,6 +976,9 @@ void RawImageSource::correction_YIQ_LQ  (Image16* im, int times) {
     		else
     			correction_YIQ_LQ_ (im, 1 + tid*blk, im->height - 1);
     	}
+#else
+    	correction_YIQ_LQ_ (im, 1 , im->height - 1);
+#endif
     }
 }
 
@@ -1807,6 +1813,7 @@ void RawImageSource::hphd_demosaic () {
     memset(hpmap[i], 0, W*sizeof(float));
   }
   
+#ifdef _OPENMP
   #pragma omp parallel
   {
 		int tid = omp_get_thread_num();
@@ -1818,7 +1825,9 @@ void RawImageSource::hphd_demosaic () {
 		else
 			hphd_vertical (hpmap, tid*blk, W);
   }
-
+#else
+  hphd_vertical (hpmap, 0, W);
+#endif
   if (plistener) 
     plistener->setProgress (0.33);
 
@@ -1826,6 +1835,7 @@ void RawImageSource::hphd_demosaic () {
   for (int i=0; i<H; i++)
     memset(this->hpmap[i], 0, W*sizeof(char));
 
+#ifdef _OPENMP
   #pragma omp parallel
   {
 		int tid = omp_get_thread_num();
@@ -1837,7 +1847,9 @@ void RawImageSource::hphd_demosaic () {
 		else
 			hphd_horizontal (hpmap, tid*blk, H);
   }
-
+#else
+  hphd_horizontal (hpmap, 0, H);
+#endif
   freeArray<float>(hpmap, H);
 
   if (plistener) 
diff --git a/rtengine/rtthumbnail.cc b/rtengine/rtthumbnail.cc
index d26a25e66..e967c08f3 100644
--- a/rtengine/rtthumbnail.cc
+++ b/rtengine/rtthumbnail.cc
@@ -794,6 +794,7 @@ bool Thumbnail::writeData  (const Glib::ustring& fname) {
     SafeKeyFile keyFile;
 
     try {
+    if( Glib::file_test(fname,Glib::FILE_TEST_EXISTS) )
         keyFile.load_from_file (fname); 
     } catch (...) {}
 
diff --git a/rtengine/shmap.cc b/rtengine/shmap.cc
index 308bf0823..6bcb4dcbf 100644
--- a/rtengine/shmap.cc
+++ b/rtengine/shmap.cc
@@ -53,14 +53,18 @@ void SHMap::update (Image16* img, unsigned short** buffer, double radius, double
 		}
 
     if (!hq) {
+#ifdef _OPENMP
     	AlignedBuffer<double>* buffer = new AlignedBuffer<double> (MAX(W,H)*omp_get_max_threads());
-
+#else
+    	AlignedBuffer<double>* buffer = new AlignedBuffer<double> (MAX(W,H));
+#endif
     	gaussHorizontal<unsigned short> (map, map, buffer, W, H, radius, multiThread);
 		gaussVertical<unsigned short>   (map, map, buffer, W, H, radius, multiThread);
 
         delete buffer;
     }
     else {
+#ifdef _OPENMP
 		#pragma omp parallel if (multiThread)
     	{
     		int tid = omp_get_thread_num();
@@ -72,6 +76,9 @@ void SHMap::update (Image16* img, unsigned short** buffer, double radius, double
     		else
     			bilateral<unsigned short> (map, buffer, W, H, 8000, radius, tid*blk, H);
 		}
+#else
+    	bilateral<unsigned short> (map, buffer, W, H, 8000, radius, 0, H);
+#endif
         // anti-alias filtering the result
         for (int i=0; i<H; i++)
             for (int j=0; j<W; j++)
diff --git a/rtgui/options.cc b/rtgui/options.cc
index 29aac88d1..1c266316c 100644
--- a/rtgui/options.cc
+++ b/rtgui/options.cc
@@ -139,7 +139,9 @@ int Options::readFromFile (Glib::ustring fname) {
 
     rtengine::SafeKeyFile keyFile;
 
-    try {    
+    try {
+    	if( !Glib::file_test(fname,Glib::FILE_TEST_EXISTS))
+    		return 1;
         if (!keyFile.load_from_file (fname)) 
             return 1;
     }