Index: trunk/psModules/src/imcombine/pmSubtractionStamps.c
===================================================================
--- trunk/psModules/src/imcombine/pmSubtractionStamps.c	(revision 14533)
+++ trunk/psModules/src/imcombine/pmSubtractionStamps.c	(revision 14534)
@@ -307,10 +307,10 @@
 {
     PS_ASSERT_ARRAY_NON_NULL(stamps, false);
-    PS_ASSERT_FLOAT_LARGER_THAN(sigma, 0.0, false);
+    PS_ASSERT_FLOAT_LARGER_THAN(fwhm, 0.0, false);
     PS_ASSERT_INT_NONNEGATIVE(footprint, false);
 
     int size = kernels->size + footprint; // Size of postage stamps
     int num = stamps->n;                // Number of stamps
-    float sigma = fwhm / (2.0 * sqrtf(2.0 * ln(2.0))); // Gaussian sigma
+    float sigma = fwhm / (2.0 * sqrtf(2.0 * log(2.0))); // Gaussian sigma
 
     for (int i = 0; i < num; i++) {