diff --git a/cranelift/filetests/filetests/preopt/constant_fold.clif b/cranelift/filetests/filetests/preopt/constant_fold.clif
new file mode 100644
index 0000000000..f0ea9539ba
--- /dev/null
+++ b/cranelift/filetests/filetests/preopt/constant_fold.clif
@@ -0,0 +1,19 @@
+test preopt
+target x86_64
+
+function %constant_fold(f64) -> f64 {
+ebb0(v0: f64):
+    v1 = f64const 0x1.0000000000000p0
+    v2 = f64const 0x1.0000000000000p1
+    v3 = fadd v1, v2
+    v4 = fadd v3, v0
+    return v4
+}
+; sameln: function %constant_fold(f64) -> f64 fast {
+; nextln: ebb0(v0: f64):
+; nextln:     v1 = f64const 0x1.0000000000000p0
+; nextln:     v2 = f64const 0x1.0000000000000p1
+; nextln:     v3 = f64const 0x1.8000000000000p1
+; nextln:     v4 = fadd v3, v0
+; nextln:     return v4
+; nextln: }
diff --git a/cranelift/preopt/src/constant_folding.rs b/cranelift/preopt/src/constant_folding.rs
index 2d7c1c2dbb..018ac04a7e 100644
--- a/cranelift/preopt/src/constant_folding.rs
+++ b/cranelift/preopt/src/constant_folding.rs
@@ -2,7 +2,7 @@
 
 use cranelift_codegen::{
     cursor::{Cursor, FuncCursor},
-    ir::{self, InstBuilder},
+    ir::{self, dfg::ValueDef, InstBuilder},
 };
 // use rustc_apfloat::{
 //     ieee::{Double, Single},
@@ -69,7 +69,10 @@ pub fn fold_constants(func: &mut ir::Function) {
 fn resolve_value_to_imm(dfg: &ir::DataFlowGraph, value: ir::Value) -> Option<ConstImm> {
     let original = dfg.resolve_aliases(value);
 
-    let inst = dfg.value_def(original).unwrap_inst();
+    let inst = match dfg.value_def(original) {
+        ValueDef::Result(inst, _) => inst,
+        ValueDef::Param(_, _) => return None,
+    };
 
     use self::ir::{InstructionData::*, Opcode::*};
     match dfg[inst] {