diff --git a/lib/ARCMigrate/FileRemapper.cpp b/lib/ARCMigrate/FileRemapper.cpp
index 474ce7d..e9b49b3 100644
--- a/lib/ARCMigrate/FileRemapper.cpp
+++ b/lib/ARCMigrate/FileRemapper.cpp
@@ -77,7 +77,9 @@ bool FileRemapper::initFromFile(StringRef filePath, DiagnosticsEngine &Diag,
   for (unsigned idx = 0; idx+3 <= lines.size(); idx += 3) {
     StringRef fromFilename = lines[idx];
     unsigned long long timeModified;
-    lines[idx+1].getAsInteger(10, timeModified);
+    if (lines[idx+1].getAsInteger(10, timeModified))
+      return report("Invalid file data: '" + lines[idx+1] + "' not a number",
+                    Diag);
     StringRef toFilename = lines[idx+2];
     
     const FileEntry *origFE = FileMgr->getFile(fromFilename);