diff --git a/packages/babel-plugin-transform-es2015-block-scoping/src/index.js b/packages/babel-plugin-transform-es2015-block-scoping/src/index.js
index 6f21235196..eb27618ae3 100644
--- a/packages/babel-plugin-transform-es2015-block-scoping/src/index.js
+++ b/packages/babel-plugin-transform-es2015-block-scoping/src/index.js
@@ -524,7 +524,11 @@ class BlockScoping {
     //
     for (let i = 0; i < declarators.length; i++) {
       let declar = declarators[i];
-      let keys = t.getBindingIdentifiers(declar);
+      // Passing true as the third argument causes t.getBindingIdentifiers
+      // to return only the *outer* binding identifiers of this
+      // declaration, rather than (for example) mistakenly including the
+      // parameters of a function declaration. Fixes #4880.
+      let keys = t.getBindingIdentifiers(declar, false, true);
       extend(this.letReferences, keys);
       this.hasLetReferences = true;
     }
diff --git a/packages/babel-plugin-transform-es2015-block-scoping/test/fixtures/general/function-in-catch/actual.js b/packages/babel-plugin-transform-es2015-block-scoping/test/fixtures/general/function-in-catch/actual.js
new file mode 100644
index 0000000000..c38a4caa3a
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-block-scoping/test/fixtures/general/function-in-catch/actual.js
@@ -0,0 +1,7 @@
+try {
+  foo();
+} catch (x) {
+  function harmless(x) {
+    return x;
+  }
+}
diff --git a/packages/babel-plugin-transform-es2015-block-scoping/test/fixtures/general/function-in-catch/expected.js b/packages/babel-plugin-transform-es2015-block-scoping/test/fixtures/general/function-in-catch/expected.js
new file mode 100644
index 0000000000..9403930476
--- /dev/null
+++ b/packages/babel-plugin-transform-es2015-block-scoping/test/fixtures/general/function-in-catch/expected.js
@@ -0,0 +1,7 @@
+try {
+  foo();
+} catch (x) {
+  var harmless = function (x) {
+    return x;
+  };
+}