diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 3614333037c4..8630ef842b4a 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -137,8 +137,13 @@ MachineInstrBuilder MachineIRBuilder::buildConstDbgValue(const Constant &C,
       MIB.addCImm(CI);
     else
       MIB.addImm(CI->getZExtValue());
-  } else
+  } else if (auto *CFP = dyn_cast<ConstantFP>(&C)) {
+    assert(isa<ConstantFP>(C) && "Unexpected constant dbg value");
     MIB.addFPImm(&cast<ConstantFP>(C));
+  } else {
+    // Insert %noreg if we didn't find a usable constant and had to drop it.
+    MIB.addReg(0U);
+  }
 
   return MIB.addImm(Offset).addMetadata(Variable).addMetadata(Expr);
 }
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/debug-insts.ll b/llvm/test/CodeGen/AArch64/GlobalISel/debug-insts.ll
index ffd2c0c68b10..2c3def2e4a9c 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/debug-insts.ll
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/debug-insts.ll
@@ -26,6 +26,8 @@ define void @debug_value(i32 %in) #0 !dbg !7 {
   call void @llvm.dbg.value(metadata i32 123, i64 0, metadata !11, metadata !12), !dbg !13
 ; CHECK: DBG_VALUE float 1.000000e+00, 0, !11, !12, debug-location !13
   call void @llvm.dbg.value(metadata float 1.000000e+00, i64 0, metadata !11, metadata !12), !dbg !13
+; CHECK: DBG_VALUE _, 0, !11, !12, debug-location !13
+  call void @llvm.dbg.value(metadata i32* null, i64 0, metadata !11, metadata !12), !dbg !13
   ret void
 }