Index: lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
===================================================================
--- lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
+++ lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
@@ -322,6 +322,8 @@
   }
 
   bool isSImm6() const {
+    if (!isImm())
+      return false;
     RISCVMCExpr::VariantKind VK;
     int64_t Imm;
     bool IsValid;
@@ -335,6 +337,8 @@
   }
 
   bool isSImm6NonZero() const {
+    if (!isImm())
+      return false;
     RISCVMCExpr::VariantKind VK;
     int64_t Imm;
     bool IsValid;
@@ -348,6 +352,8 @@
   }
 
   bool isCLUIImm() const {
+    if (!isImm())
+      return false;
     int64_t Imm;
     RISCVMCExpr::VariantKind VK;
     bool IsConstantImm = evaluateConstantImm(Imm, VK);
@@ -357,6 +363,8 @@
   }
 
   bool isUImm7Lsb00() const {
+    if (!isImm())
+      return false;
     int64_t Imm;
     RISCVMCExpr::VariantKind VK;
     bool IsConstantImm = evaluateConstantImm(Imm, VK);
@@ -365,6 +373,8 @@
   }
 
   bool isUImm8Lsb00() const {
+    if (!isImm())
+      return false;
     int64_t Imm;
     RISCVMCExpr::VariantKind VK;
     bool IsConstantImm = evaluateConstantImm(Imm, VK);
@@ -373,6 +383,8 @@
   }
 
   bool isUImm8Lsb000() const {
+    if (!isImm())
+      return false;
     int64_t Imm;
     RISCVMCExpr::VariantKind VK;
     bool IsConstantImm = evaluateConstantImm(Imm, VK);
@@ -383,6 +395,8 @@
   bool isSImm9Lsb0() const { return isBareSimmNLsb0<9>(); }
 
   bool isUImm9Lsb000() const {
+    if (!isImm())
+      return false;
     int64_t Imm;
     RISCVMCExpr::VariantKind VK;
     bool IsConstantImm = evaluateConstantImm(Imm, VK);
Index: test/MC/RISCV/rv32c-fuzzed-invalid.s
===================================================================
--- /dev/null
+++ test/MC/RISCV/rv32c-fuzzed-invalid.s
@@ -0,0 +1,14 @@
+# REQUIRES: asserts
+# RUN: not llvm-mc -triple riscv32 -mattr=+c,+f,+d < %s 2>&1 | FileCheck %s
+#
+# Fuzzed test cases produced by a LLVM MC Assembler
+# Protocol Buffer Fuzzer for the RISC-V assembly language.
+#
+c.addi x13,f30,0 # CHECK: error: immediate must be non-zero in the range [-32, 31]
+c.swsp  x0,(f14) # CHECK: error: immediate must be a multiple of 4 bytes in the range [0, 252]
+c.lui   x4,x0    # CHECK: error: immediate must be in [0xfffe0, 0xfffff] or [1, 31]
+
+c.fsdsp f9,x0,0    # CHECK: error: immediate must be a multiple of 8 bytes in the range [0, 504]
+c.flw   f15,x14,x0 # CHECK: error: immediate must be a multiple of 4 bytes in the range [0, 124]
+c.fld   f8,f30,x17 # CHECK: error: immediate must be a multiple of 8 bytes in the range [0, 248]
+c.li    x6,x6,x0,x0 # CHECK: error: immediate must be an integer in the range [-32, 31]