diff --git a/help.c b/help.c
index 2ff3b5a774..0f5fc33748 100644
--- a/help.c
+++ b/help.c
@@ -105,7 +105,16 @@ static int is_executable(const char *name)
 		return 0;
 
 #if defined(GIT_WINDOWS_NATIVE)
-{	/* cannot trust the executable bit, peek into the file instead */
+	/* On Windows we cannot use the executable bit. The executable
+	 * state is determined by extension only. We do this first
+	 * because with virus scanners opening an executeable for
+	 * reading is potentially expensive.
+	 */
+	if (ends_with(name, ".exe"))
+		return S_IXUSR;
+
+{	/* now that we know it does not have an executable extension,
+	   peek into the file instead */
 	char buf[3] = { 0 };
 	int n;
 	int fd = open(name, O_RDONLY);
@@ -113,8 +122,8 @@ static int is_executable(const char *name)
 	if (fd >= 0) {
 		n = read(fd, buf, 2);
 		if (n == 2)
-			/* DOS executables start with "MZ" */
-			if (!strcmp(buf, "#!") || !strcmp(buf, "MZ"))
+			/* look for a she-bang */
+			if (!strcmp(buf, "#!"))
 				st.st_mode |= S_IXUSR;
 		close(fd);
 	}