diff --git a/src/fix/main.c b/src/fix/main.c
index 1a872c96..dc5a3f3c 100644
--- a/src/fix/main.c
+++ b/src/fix/main.c
@@ -967,6 +967,10 @@ static void processFile(int input, int output, char const *name, off_t fileSize)
 
 	if (oldLicensee != UNSPECIFIED)
 		overwriteByte(rom0, 0x14B, oldLicensee, "old licensee code");
+	else if (sgb && rom0[0x14B] != 0x33)
+		fprintf(stderr,
+			"warning: SGB compatibility enabled, but old licensee was %#x, not 0x33\n",
+			rom0[0x14B]);
 
 	if (romVersion != UNSPECIFIED)
 		overwriteByte(rom0, 0x14C, romVersion, "mask ROM version number");
diff --git a/test/fix/sgb-old-licensee.bin b/test/fix/sgb-old-licensee.bin
new file mode 100644
index 00000000..929bea12
Binary files /dev/null and b/test/fix/sgb-old-licensee.bin differ
diff --git a/test/fix/sgb-old-licensee.err b/test/fix/sgb-old-licensee.err
new file mode 100644
index 00000000..2edaa257
--- /dev/null
+++ b/test/fix/sgb-old-licensee.err
@@ -0,0 +1,2 @@
+warning: Overwrote a non-zero byte in the SGB flag
+warning: SGB compatibility enabled, but old licensee was 0xc5, not 0x33
diff --git a/test/fix/sgb-old-licensee.flags b/test/fix/sgb-old-licensee.flags
new file mode 100644
index 00000000..5d9af957
--- /dev/null
+++ b/test/fix/sgb-old-licensee.flags
@@ -0,0 +1 @@
+-s
diff --git a/test/fix/sgb.bin b/test/fix/sgb.bin
index 3ab8ec34..28a68032 100644
Binary files a/test/fix/sgb.bin and b/test/fix/sgb.bin differ
diff --git a/test/fix/sgb.gb b/test/fix/sgb.gb
index 4cf70bb6..7816b245 100644
Binary files a/test/fix/sgb.gb and b/test/fix/sgb.gb differ