diff --git a/nmake.opt b/nmake.opt
index 88e197c..308eddd 100644
--- a/nmake.opt
+++ b/nmake.opt
@@ -147,11 +147,21 @@ CXX_PDB_FLAGS=/Zi /Fd$(GDAL_PDB)
 CXX_PDB_FLAGS=
 !ENDIF
 
+# Flags to choose CRT variant to link against (e.g. static: /MT, /MTd, dynamic: /MD, /MDd)
+# Ensure MRSID_CONFIG in mrsid/nmake.opt is set appropriately as well
+!IFNDEF CXX_CRT_FLAGS
+!IFNDEF DEBUG
+CXX_CRT_FLAGS=/MD
+!ELSE
+CXX_CRT_FLAGS=/MDd
+!ENDIF
+!ENDIF
+
 !IFNDEF OPTFLAGS
 !IF "$(DEBUG)" == "0"
-OPTFLAGS= $(CXX_ANALYZE_FLAGS) $(CXX_PDB_FLAGS) /nologo /MP$(CPU_COUNT) /MD /EHsc /Ox /FC /D_CRT_SECURE_NO_DEPRECATE /D_CRT_NONSTDC_NO_DEPRECATE /DNDEBUG
+OPTFLAGS= $(CXX_ANALYZE_FLAGS) $(CXX_PDB_FLAGS) /nologo /MP$(CPU_COUNT) $(CXX_CRT_FLAGS) /EHsc /Ox /D_CRT_SECURE_NO_DEPRECATE /D_CRT_NONSTDC_NO_DEPRECATE /DNDEBUG
 !ELSE
-OPTFLAGS= $(CXX_ANALYZE_FLAGS) $(CXX_PDB_FLAGS) /nologo /MP$(CPU_COUNT) /MDd /EHsc /FC /D_CRT_SECURE_NO_DEPRECATE /D_CRT_NONSTDC_NO_DEPRECATE /DDEBUG
+OPTFLAGS= $(CXX_ANALYZE_FLAGS) $(CXX_PDB_FLAGS) /nologo /MP$(CPU_COUNT) $(CXX_CRT_FLAGS) /EHsc /D_CRT_SECURE_NO_DEPRECATE /D_CRT_NONSTDC_NO_DEPRECATE /DDEBUG
 !ENDIF
 !ENDIF  # OPTFLAGS