diff --git a/src/corrupter.c b/src/corrupter.c
index 64cb960..551c508 100644
--- a/src/corrupter.c
+++ b/src/corrupter.c
@@ -132,8 +132,10 @@ Corrupter_Result corrupt_file(Corrupter_Param* param) {
 
 	rewind(file);
 
+	size_t file_size = end - start;
+
 	// allocate memory for the file content
-	byte* buffer = malloc(end);
+	byte* buffer = malloc(file_size * sizeof(byte));
 
 	if (buffer == NULL) {
 		PERROR_MACRO("malloc");
@@ -156,7 +158,7 @@ Corrupter_Result corrupt_file(Corrupter_Param* param) {
 	}
 
 	// output data to result
-	result.file_size = end - start;
+	result.file_size = file_size;
 
 	// initialize the PRNG
 	mt_seed(param->seed);