diff --git a/clang/lib/Analysis/ScanfFormatString.cpp b/clang/lib/Analysis/ScanfFormatString.cpp
index 5342259..734dc75 100644
--- a/clang/lib/Analysis/ScanfFormatString.cpp
+++ b/clang/lib/Analysis/ScanfFormatString.cpp
@@ -251,8 +251,7 @@
         case LengthModifier::AsIntMax:
           return ArgType::PtrTo(ArgType(Ctx.getIntMaxType(), "intmax_t"));
         case LengthModifier::AsSizeT:
-          // FIXME: ssize_t.
-          return ArgType();
+          return ArgType::PtrTo(ArgType(Ctx.getSignedSizeType(), "ssize_t"));
         case LengthModifier::AsPtrDiff:
           return ArgType::PtrTo(ArgType(Ctx.getPointerDiffType(), "ptrdiff_t"));
         case LengthModifier::AsLongDouble:
@@ -386,7 +385,7 @@
         case LengthModifier::AsIntMax:
           return ArgType::PtrTo(ArgType(Ctx.getIntMaxType(), "intmax_t"));
         case LengthModifier::AsSizeT:
-          return ArgType(); // FIXME: ssize_t
+          return ArgType::PtrTo(ArgType(Ctx.getSignedSizeType(), "ssize_t"));
         case LengthModifier::AsPtrDiff:
           return ArgType::PtrTo(ArgType(Ctx.getPointerDiffType(), "ptrdiff_t"));
         case LengthModifier::AsLongDouble: