diff --git a/Core/FileSystems/ISOFileSystem.cpp b/Core/FileSystems/ISOFileSystem.cpp
index fcb7390571..3f0b8c5882 100644
--- a/Core/FileSystems/ISOFileSystem.cpp
+++ b/Core/FileSystems/ISOFileSystem.cpp
@@ -201,7 +201,7 @@ ISOFileSystem::~ISOFileSystem() {
 }
 
 void ISOFileSystem::ReadDirectory(TreeEntry *root) {
-	for (u32 secnum = root->startsector, endsector = root->startsector + root->dirsize /2048; secnum < endsector; ++secnum) {
+	for (u32 secnum = root->startsector, endsector = root->startsector + (root->dirsize + 2047) / 2048; secnum < endsector; ++secnum) {
 		u8 theSector[2048];
 		if (!blockDevice->ReadBlock(secnum, theSector)) {
 			ERROR_LOG(FILESYS, "Error reading block for directory %s - skipping", root->name.c_str());
@@ -233,10 +233,10 @@ void ISOFileSystem::ReadDirectory(TreeEntry *root) {
 			if (dir.identifierLength == 1 && (dir.firstIdChar == '\x00' || dir.firstIdChar == '.')) {
 				entry->name = ".";
 				relative = true;
-			}	else if (dir.identifierLength == 1 && dir.firstIdChar == '\x01')			{
+			} else if (dir.identifierLength == 1 && dir.firstIdChar == '\x01') {
 				entry->name = "..";
 				relative = true;
-			}	else {
+			} else {
 				entry->name = std::string((const char *)&dir.firstIdChar, dir.identifierLength);
 				relative = false;
 			}
@@ -250,7 +250,7 @@ void ISOFileSystem::ReadDirectory(TreeEntry *root) {
 			entry->dirsize = dir.dataLength();
 			entry->valid = isFile;  // Can pre-mark as valid if file, as we don't recurse into those.
 			// Let's not excessively spam the log - I commented this line out.
-			//DEBUG_LOG(FILESYS, "%s: %s %08x %08x %i", e->isDirectory?"D":"F", e->name.c_str(), dir.firstDataSectorLE, e->startingPosition, e->startingPosition);
+			//DEBUG_LOG(FILESYS, "%s: %s %08x %08x %i", entry->isDirectory?"D":"F", entry->name.c_str(), dir.firstDataSectorLE, entry->startingPosition, entry->startingPosition);
 
 			if (entry->isDirectory && !relative) {
 				if (entry->startsector == root->startsector) {
diff --git a/Core/PSPLoaders.cpp b/Core/PSPLoaders.cpp
index e6eaa00c74..1e51bae050 100644
--- a/Core/PSPLoaders.cpp
+++ b/Core/PSPLoaders.cpp
@@ -231,6 +231,24 @@ bool Load_PSP_ISO(FileLoader *fileLoader, std::string *error_string)
 		// try unencrypted BOOT.BIN
 		bootpath = "disc0:/PSP_GAME/SYSDIR/BOOT.BIN";
 	}
+
+	// Fail early with a clearer message for some types of ISOs.
+	if (!pspFileSystem.GetFileInfo(bootpath).exists) {
+		// Can't tell for sure if it's PS1 or PS2, but doesn't much matter.
+		if (pspFileSystem.GetFileInfo("disc0:/SYSTEM.CNF;1").exists || pspFileSystem.GetFileInfo("disc0:/PSX.EXE;1").exists) {
+			*error_string = "PPSSPP plays PSP games, not Playstation 1 or 2 games.";
+		} else if (pspFileSystem.GetFileInfo("disc0:/UMD_VIDEO/PLAYLIST.UMD").exists) {
+			*error_string = "PPSSPP doesn't support UMD Video.";
+		} else if (pspFileSystem.GetFileInfo("disc0:/UMD_AUDIO/PLAYLIST.UMD").exists) {
+			*error_string = "PPSSPP doesn't support UMD Music.";
+		} else if (pspFileSystem.GetDirListing("disc0:/").empty()) {
+			*error_string = "Not a valid disc image.";
+		} else {
+			*error_string = "A PSP game couldn't be found on the disc.";
+		}
+		return false;
+	}
+
 	//in case we didn't go through EmuScreen::boot
 	g_Config.loadGameConfig(id);
 	INFO_LOG(LOADER,"Loading %s...", bootpath.c_str());