diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 53c44d3f..0e49efca 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,7 +7,7 @@ jobs:
   test:
     strategy:
       matrix:
-        node: [ '0.10', '0.12', '4', '6', '8', '10', '12', '14', '16', latest ]
+        node: [ '0.10', '0.12', '4', '6', '8', '10', '12', '14', '16', '18' ]
         os: [ ubuntu-latest, windows-latest ]
         script: [ compress, mocha, release/benchmark, release/jetstream ]
     name: ${{ matrix.node }} ${{ matrix.os }} ${{ matrix.script }}
diff --git a/lib/compress.js b/lib/compress.js
index d7723c00..034a9e03 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -7498,6 +7498,7 @@ Compressor.prototype.compress = function(node) {
                             });
                             body.push(defun);
                             if (value !== fn) [].push.apply(side_effects, value.expressions.slice(0, -1));
+                            sym.eliminated++;
                         } else {
                             if (drop_sym
                                 && var_defs[sym.id] > 1
@@ -14065,8 +14066,12 @@ Compressor.prototype.compress = function(node) {
                 def.single_use = false;
                 if (!in_loop) return;
                 if (def.references.length == def.replaced) return;
-                if (def.orig.length == def.eliminated) return;
-                if (def.orig.length == 1 && fn.functions.has(name)) return;
+                switch (def.orig.length - def.eliminated) {
+                  case 0:
+                    return;
+                  case 1:
+                    if (fn.functions.has(name)) return;
+                }
                 if (!all(def.orig, function(sym) {
                     if (sym instanceof AST_SymbolConst) return false;
                     if (sym instanceof AST_SymbolFunarg) return !sym.unused && def.scope.resolve() !== fn;
diff --git a/test/compress/functions.js b/test/compress/functions.js
index 8a46879c..e0d504d7 100644
--- a/test/compress/functions.js
+++ b/test/compress/functions.js
@@ -8741,3 +8741,79 @@ issue_5692: {
     }
     expect_stdout: "PASS"
 }
+
+issue_5766_1: {
+    options = {
+        booleans: true,
+        evaluate: true,
+        functions: true,
+        inline: true,
+        passes: 2,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        log = function(a) {
+            console.log(typeof a);
+        };
+        do {
+            (function() {
+                try {
+                    var f = function() {};
+                    log(f && f);
+                } catch (e) {}
+            })();
+        } while (0);
+    }
+    expect: {
+        log = function(a) {
+            console.log(typeof a);
+        };
+        do {
+            try {
+                function f() {}
+                log(f);
+            } catch (e) {}
+        } while (0);
+    }
+    expect_stdout: "function"
+}
+
+issue_5766_2: {
+    options = {
+        evaluate: true,
+        functions: true,
+        inline: true,
+        passes: 2,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        log = function(a) {
+            console.log(typeof a);
+        };
+        do {
+            (function() {
+                try {
+                    var f = function() {};
+                    log(f && f);
+                } catch (e) {}
+            })();
+        } while (0);
+    }
+    expect: {
+        log = function(a) {
+            console.log(typeof a);
+        };
+        do {
+            try {
+                function f() {}
+                log(f);
+            } catch (e) {}
+        } while (0);
+    }
+    expect_stdout: "function"
+}