diff --git a/BasiliskII/src/Unix/main_unix.cpp b/BasiliskII/src/Unix/main_unix.cpp
index c80f95f4..59444580 100644
--- a/BasiliskII/src/Unix/main_unix.cpp
+++ b/BasiliskII/src/Unix/main_unix.cpp
@@ -432,12 +432,14 @@ int main(int argc, char **argv)
 #if defined(__APPLE__) && defined(__MACH__)
 		// Mac OS X likes to pass in various options of its own, when launching an app.
 		// Attempt to ignore these.
-		const char * mac_psn_prefix = "-psn_";
-		if (strcmp(argv[i], "-NSDocumentRevisionsDebugMode") == 0) {
-			argv[i] = NULL;
-		} else if (strncmp(mac_psn_prefix, argv[i], strlen(mac_psn_prefix)) == 0) {
-			argv[i] = NULL;
-		}
+        if (argv[i]) {
+            const char * mac_psn_prefix = "-psn_";
+            if (strcmp(argv[i], "-NSDocumentRevisionsDebugMode") == 0) {
+                argv[i] = NULL;
+            } else if (strncmp(mac_psn_prefix, argv[i], strlen(mac_psn_prefix)) == 0) {
+                argv[i] = NULL;
+            }
+        }
 #endif
 	}