diff --git a/lib/environ/src/cranelift.rs b/lib/environ/src/cranelift.rs
index 573b8b1322..7cc35a9aac 100644
--- a/lib/environ/src/cranelift.rs
+++ b/lib/environ/src/cranelift.rs
@@ -87,8 +87,8 @@ pub fn compile_module<'data, 'module>(
     function_body_inputs: PrimaryMap<DefinedFuncIndex, &'data [u8]>,
     isa: &dyn isa::TargetIsa,
 ) -> Result<(Compilation, Relocations), CompileError> {
-    let mut functions = PrimaryMap::new();
-    let mut relocations = PrimaryMap::new();
+    let mut functions = PrimaryMap::with_capacity(function_body_inputs.len());
+    let mut relocations = PrimaryMap::with_capacity(function_body_inputs.len());
     for (i, input) in function_body_inputs.into_iter() {
         let func_index = module.func_index(i);
         let mut context = Context::new();