diff --git a/lib/compress.js b/lib/compress.js
index af462ba9..7729ffde 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -8055,8 +8055,16 @@ Compressor.prototype.compress = function(node) {
             if (!compressor.option("awaits")) return this;
             var exp = this.expression;
             if (!is_primitive(compressor, exp)) return this;
+            if (exp instanceof AST_UnaryPrefix && exp.operator == "!") exp = exp.expression;
+            var dropped = exp.drop_side_effect_free(compressor);
+            if (dropped === exp) return this;
+            if (!dropped) {
+                dropped = make_node(AST_Number, exp, { value: 0 });
+            } else if (!is_primitive(compressor, dropped)) {
+                dropped = dropped.negate(compressor);
+            }
             var node = this.clone();
-            node.expression = exp.drop_side_effect_free(compressor) || make_node(AST_Number, this, { value: 0 });
+            node.expression = dropped;
             return node;
         });
         def(AST_Binary, function(compressor, first_in_statement) {
@@ -8400,7 +8408,8 @@ Compressor.prototype.compress = function(node) {
             if (compressor.option("awaits") && end > 0 && last instanceof AST_Await && last.expression.is_constant()) {
                 expressions = expressions.slice(0, -1);
                 end--;
-                last.expression = expressions[end];
+                var expr = expressions[end];
+                last.expression = is_primitive(compressor, expr) ? expr : expr.negate(compressor);
                 expressions[end] = last;
             }
             var assign, cond, lhs;
@@ -10728,13 +10737,7 @@ Compressor.prototype.compress = function(node) {
         if (compressor.option("side_effects")) {
             var exp = self.expression;
             if (exp instanceof AST_Await) return exp.optimize(compressor);
-            if (exp instanceof AST_UnaryPrefix) {
-                if (exp.expression instanceof AST_Await) return exp.optimize(compressor);
-                if (exp.operator == "void") return make_node(AST_UnaryPrefix, self, {
-                    operator: "void",
-                    expression: make_node(AST_Await, self, { expression: exp.expression }),
-                }).optimize(compressor);
-            }
+            if (exp instanceof AST_UnaryPrefix && exp.expression instanceof AST_Await) return exp.optimize(compressor);
             for (var level = 0, node = self, parent; parent = compressor.parent(level++); node = parent) {
                 if (is_arrow(parent)) {
                     if (parent.value === node) return exp.optimize(compressor);
diff --git a/test/compress/awaits.js b/test/compress/awaits.js
index 68459fab..91c5c3ef 100644
--- a/test/compress/awaits.js
+++ b/test/compress/awaits.js
@@ -693,7 +693,124 @@ inline_block_return_async: {
     node_version: ">=8"
 }
 
-await_unary: {
+await_then: {
+    options = {
+        awaits: true,
+        side_effects: true,
+    }
+    input: {
+        var a = "PASS";
+        function f() {
+            return {
+                then: function(r) {
+                    a = "FAIL";
+                    r();
+                },
+            };
+        }
+        (async function() {
+            f(), await 42;
+            while (console.log(a));
+        })();
+    }
+    expect: {
+        var a = "PASS";
+        function f() {
+            return {
+                then: function(r) {
+                    a = "FAIL";
+                    r();
+                },
+            };
+        }
+        (async function() {
+            await !f();
+            while (console.log(a));
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}
+
+await_unary_1: {
+    options = {
+        awaits: true,
+        side_effects: true,
+    }
+    input: {
+        var a = "PASS";
+        function f() {
+            return {
+                then: function(r) {
+                    a = "FAIL";
+                    r();
+                },
+            };
+        }
+        (async function() {
+            await !f();
+            while (console.log(a));
+        })();
+    }
+    expect: {
+        var a = "PASS";
+        function f() {
+            return {
+                then: function(r) {
+                    a = "FAIL";
+                    r();
+                },
+            };
+        }
+        (async function() {
+            await !f();
+            while (console.log(a));
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}
+
+await_unary_2: {
+    options = {
+        awaits: true,
+        side_effects: true,
+    }
+    input: {
+        var a = "PASS";
+        function f() {
+            return {
+                then: function(r) {
+                    a = "FAIL";
+                    r();
+                },
+            };
+        }
+        (async function() {
+            await ~f();
+            while (console.log(a));
+        })();
+    }
+    expect: {
+        var a = "PASS";
+        function f() {
+            return {
+                then: function(r) {
+                    a = "FAIL";
+                    r();
+                },
+            };
+        }
+        (async function() {
+            await !f();
+            while (console.log(a));
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}
+
+await_unary_3: {
     options = {
         awaits: true,
         side_effects: true,
@@ -720,7 +837,46 @@ await_unary: {
     node_version: ">=8"
 }
 
-await_void: {
+await_void_1: {
+    options = {
+        awaits: true,
+        side_effects: true,
+    }
+    input: {
+        var a = "PASS";
+        function f() {
+            return {
+                then: function(r) {
+                    a = "FAIL";
+                    r();
+                },
+            };
+        }
+        (async function() {
+            await void f();
+            while (console.log(a));
+        })();
+    }
+    expect: {
+        var a = "PASS";
+        function f() {
+            return {
+                then: function(r) {
+                    a = "FAIL";
+                    r();
+                },
+            };
+        }
+        (async function() {
+            await !f();
+            while (console.log(a));
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}
+
+await_void_2: {
     options = {
         awaits: true,
         if_return: true,
@@ -735,7 +891,7 @@ await_void: {
     }
     expect: {
         (async function() {
-            await console.log("PASS");
+            console.log("PASS");
         })();
     }
     expect_stdout: "PASS"