diff --git a/prism/src/mtbdd/PrismMTBDD.cc b/prism/src/mtbdd/PrismMTBDD.cc
index 2cc2bec5..5a7ec1a8 100644
--- a/prism/src/mtbdd/PrismMTBDD.cc
+++ b/prism/src/mtbdd/PrismMTBDD.cc
@@ -210,7 +210,7 @@ void export_string(const char *str, ...)
 	if (export_file) {
 		fprintf(export_file, "%s", full_string);
 	} else {
-		PM_PrintToMainLog(export_env, full_string);
+		PM_PrintToMainLog(export_env, "%s", full_string);
 	}
 }
 
diff --git a/prism/src/sparse/PrismSparse.cc b/prism/src/sparse/PrismSparse.cc
index bd0bc6e7..f7dfe139 100644
--- a/prism/src/sparse/PrismSparse.cc
+++ b/prism/src/sparse/PrismSparse.cc
@@ -234,7 +234,7 @@ void export_string(const char *str, ...)
 	if (export_file) {
 		fprintf(export_file, "%s", full_string);
 	} else {
-		PS_PrintToMainLog(export_env, full_string);
+		PS_PrintToMainLog(export_env, "%s", full_string);
 	}
 }