1 files changed, 2 insertions, 1 deletions
diff --git a/src/main.c b/src/main.c
index a1b79f3..74cdef9 100644
--- a/src/main.c
+++ b/src/main.c
@@ -193,7 +193,8 @@ int main(int argc, char *argv[])
     };
 
     float *kernel = NULL;
-    if (!strcmp(filter, "edge")) kernel = edge;
+    if (!filter) usage();
+    else if (!strcmp(filter, "edge")) kernel = edge;
     else if (!strcmp(filter, "blur")) kernel = blur;
     else if (!strcmp(filter, "sharpen")) kernel = sharpen;
     else usage();