diff --git a/tools/scan_includes.c b/tools/scan_includes.c
index 826af56cc..9ec5f3c5d 100644
--- a/tools/scan_includes.c
+++ b/tools/scan_includes.c
@@ -3,6 +3,8 @@
 
 #include "common.h"
 
+#include <ctype.h>
+
 void parse_args(int argc, char *argv[], bool *strict) {
 	struct option long_options[] = {
 		{"strict", no_argument, 0, 's'},
@@ -40,8 +42,7 @@ void scan_file(const char *filename, bool strict) {
 	fclose(f);
 	contents[size] = '\0';
 
-	for (char *ptr = contents; ptr && ptr - contents < size; ptr++) {
-		bool is_incbin = false, is_include = false;
+	for (char *ptr = contents; ptr && ptr < contents + size; ptr++) {
 		ptr = strpbrk(ptr, ";\"Ii");
 		if (!ptr) {
 			break;
@@ -49,36 +50,34 @@ void scan_file(const char *filename, bool strict) {
 		switch (*ptr) {
 		case ';':
 			// Skip comments until the end of the line
-			ptr = strchr(ptr + 1, '\n');
-			if (!ptr) {
-				fprintf(stderr, "%s: no newline at end of file\n", filename);
-				goto done;
-			}
-			break;
-		case '"':
-			// Skip string iteral until the closing quote
-			ptr = strchr(ptr + 1, '"');
-			if (ptr) {
+			ptr += strcspn(ptr + 1, "\r\n");
+			if (*ptr) {
 				ptr++;
-			} else {
-				fprintf(stderr, "%s: unterminated string\n", filename);
-				goto done;
 			}
 			break;
+
+		case '"':
+			// Skip string literal until the closing quote
+			ptr += strcspn(ptr + 1, "\"");
+			if (*ptr) {
+				ptr++;
+			}
+			break;
+
 		case 'I':
 		case 'i':
 			/* empty statement between the label and the variable declaration */;
 			// Check that an INCLUDE/INCBIN starts as its own token
 			char before = ptr > contents ? *(ptr - 1) : '\n';
-			if (before != ' ' && before != '\t' && before != '\n' && before != ':') {
+			if (!isspace((unsigned)before) && before != ':') {
 				break;
 			}
-			is_incbin = !strncmp(ptr, "INCBIN", 6) || !strncmp(ptr, "incbin", 6);
-			is_include = !strncmp(ptr, "INCLUDE", 7) || !strncmp(ptr, "include", 7);
+			bool is_incbin = !strncmp(ptr, "INCBIN", 6) || !strncmp(ptr, "incbin", 6);
+			bool is_include = !strncmp(ptr, "INCLUDE", 7) || !strncmp(ptr, "include", 7);
 			if (is_incbin || is_include) {
 				// Check that an INCLUDE/INCBIN ends as its own token
 				ptr += is_include ? 7 : 6;
-				if (*ptr != ' ' && *ptr != '\t' && *ptr != '\n' && *ptr != '"') {
+				if (!isspace((unsigned)*ptr) && *ptr != '"') {
 					break;
 				}
 				ptr += strspn(ptr, " \t");
@@ -105,7 +104,6 @@ void scan_file(const char *filename, bool strict) {
 		}
 	}
 
-done:
 	free(contents);
 }