diff --git a/src/util/patch-ips.c b/src/util/patch-ips.c
index 6d6d53be9..0249f9ce9 100644
--- a/src/util/patch-ips.c
+++ b/src/util/patch-ips.c
@@ -9,7 +9,7 @@
 #include "util/vfs.h"
 
 static size_t _IPSOutputSize(struct Patch* patch, size_t inSize);
-static bool _IPSApplyPatch(struct Patch* patch, void* in, size_t inSize, void* out, size_t outSize);
+static bool _IPSApplyPatch(struct Patch* patch, const void* in, size_t inSize, void* out, size_t outSize);
 
 bool loadPatchIPS(struct Patch* patch) {
 	patch->vf->seek(patch->vf, 0, SEEK_SET);
@@ -43,7 +43,7 @@ size_t _IPSOutputSize(struct Patch* patch, size_t inSize) {
 	return 16 * 1024 * 1024; // IPS patches can grow up to 16MiB, but not beyond
 }
 
-bool _IPSApplyPatch(struct Patch* patch, void* in, size_t inSize, void* out, size_t outSize) {
+bool _IPSApplyPatch(struct Patch* patch, const void* in, size_t inSize, void* out, size_t outSize) {
 	if (patch->vf->seek(patch->vf, 5, SEEK_SET) != 5) {
 		return false;
 	}
diff --git a/src/util/patch-ups.c b/src/util/patch-ups.c
index f51d4cc0a..80573387a 100644
--- a/src/util/patch-ups.c
+++ b/src/util/patch-ups.c
@@ -17,8 +17,8 @@ enum {
 
 static size_t _UPSOutputSize(struct Patch* patch, size_t inSize);
 
-static bool _UPSApplyPatch(struct Patch* patch, void* in, size_t inSize, void* out, size_t outSize);
-static bool _BPSApplyPatch(struct Patch* patch, void* in, size_t inSize, void* out, size_t outSize);
+static bool _UPSApplyPatch(struct Patch* patch, const void* in, size_t inSize, void* out, size_t outSize);
+static bool _BPSApplyPatch(struct Patch* patch, const void* in, size_t inSize, void* out, size_t outSize);
 
 static size_t _decodeLength(struct VFile* vf);
 
@@ -64,7 +64,7 @@ size_t _UPSOutputSize(struct Patch* patch, size_t inSize) {
 	return _decodeLength(patch->vf);
 }
 
-bool _UPSApplyPatch(struct Patch* patch, void* in, size_t inSize, void* out, size_t outSize) {
+bool _UPSApplyPatch(struct Patch* patch, const void* in, size_t inSize, void* out, size_t outSize) {
 	// TODO: Input checksum
 
 	size_t filesize = patch->vf->size(patch->vf);
@@ -109,7 +109,7 @@ bool _UPSApplyPatch(struct Patch* patch, void* in, size_t inSize, void* out, siz
 	return true;
 }
 
-bool _BPSApplyPatch(struct Patch* patch, void* in, size_t inSize, void* out, size_t outSize) {
+bool _BPSApplyPatch(struct Patch* patch, const void* in, size_t inSize, void* out, size_t outSize) {
 	patch->vf->seek(patch->vf, IN_CHECKSUM, SEEK_END);
 	uint32_t expectedInChecksum;
 	uint32_t expectedOutChecksum;
@@ -139,7 +139,7 @@ bool _BPSApplyPatch(struct Patch* patch, void* in, size_t inSize, void* out, siz
 	ssize_t readTargetLocation = 0;
 	size_t readOffset;
 	uint8_t* writeBuffer = out;
-	uint8_t* readBuffer = in;
+	const uint8_t* readBuffer = in;
 	while (patch->vf->seek(patch->vf, 0, SEEK_CUR) < filesize + IN_CHECKSUM) {
 		size_t command = _decodeLength(patch->vf);
 		size_t length = (command >> 2) + 1;
diff --git a/src/util/patch.h b/src/util/patch.h
index 74acaea4e..f84d859df 100644
--- a/src/util/patch.h
+++ b/src/util/patch.h
@@ -14,7 +14,7 @@ struct Patch {
 	struct VFile* vf;
 
 	size_t (*outputSize)(struct Patch* patch, size_t inSize);
-	bool (*applyPatch)(struct Patch* patch, void* in, size_t inSize, void* out, size_t outSize);
+	bool (*applyPatch)(struct Patch* patch, const void* in, size_t inSize, void* out, size_t outSize);
 };
 
 bool loadPatch(struct VFile* vf, struct Patch* patch);