diff --git a/src/expr.rs b/src/expr.rs
index 01cc388c186..dc152e46a40 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -820,9 +820,20 @@ impl<'a> ControlFlow<'a> {
                 .offset_left(matcher.len())?
                 .sub_width(self.connector.len())?;
             let pat_string = pat.rewrite(context, pat_shape)?;
-            let comments_lo = context
-                .snippet_provider
-                .span_after(self.span, self.connector.trim());
+            // When handling for loops we want to avoid incorrectly finding "in"
+            // inside the pattern so we first offset the span to start after the pattern
+            // see https://github.com/rust-lang/rustfmt/issues/5009
+            let comments_lo = if self.keyword == "for" {
+                let lo_after_pat = context.snippet_provider.span_after(self.span, &pat_string);
+
+                context
+                    .snippet_provider
+                    .span_after(self.span.with_lo(lo_after_pat), self.connector.trim())
+            } else {
+                context
+                    .snippet_provider
+                    .span_after(self.span, self.connector.trim())
+            };
             let comments_span = mk_sp(comments_lo, expr.span.lo());
             return rewrite_assign_rhs_with_comments(
                 context,
diff --git a/tests/target/issue-5009/1_minimum_example.rs b/tests/target/issue-5009/1_minimum_example.rs
new file mode 100644
index 00000000000..55836f4bf52
--- /dev/null
+++ b/tests/target/issue-5009/1_minimum_example.rs
@@ -0,0 +1,4 @@
+fn main() {
+    // the "in" inside the pattern produced invalid syntax
+    for variable_in_here /* ... */ in 0..1 {}
+}
diff --git a/tests/target/issue-5009/2_many_in_connectors_in_pattern.rs b/tests/target/issue-5009/2_many_in_connectors_in_pattern.rs
new file mode 100644
index 00000000000..d83590c6852
--- /dev/null
+++ b/tests/target/issue-5009/2_many_in_connectors_in_pattern.rs
@@ -0,0 +1,3 @@
+fn main() {
+    for in_in_in_in_in_in_in_in /* ... */ in 0..1 {}
+}
diff --git a/tests/target/issue-5009/3_nested_for_loop_with_connector_in_pattern.rs b/tests/target/issue-5009/3_nested_for_loop_with_connector_in_pattern.rs
new file mode 100644
index 00000000000..9c800723939
--- /dev/null
+++ b/tests/target/issue-5009/3_nested_for_loop_with_connector_in_pattern.rs
@@ -0,0 +1,5 @@
+fn main() {
+    for variable_in_x /* ... */ in 0..1 {
+        for variable_in_y /* ... */ in 0..1 {}
+    }
+}
diff --git a/tests/target/issue-5009/4_nested_for_loop_with_if_elseif_else.rs b/tests/target/issue-5009/4_nested_for_loop_with_if_elseif_else.rs
new file mode 100644
index 00000000000..a716d0d3082
--- /dev/null
+++ b/tests/target/issue-5009/4_nested_for_loop_with_if_elseif_else.rs
@@ -0,0 +1,13 @@
+fn main() {
+    for variable_in_x /* ... */ in 0..1 {
+        for variable_in_y /* ... */ in 0..1 {
+            if false {
+
+            } else if false {
+
+            } else {
+
+            }
+        }
+    }
+}
diff --git a/tests/target/issue-5009/5_nested_for_loop_with_connector_in_if_elseif_else.rs b/tests/target/issue-5009/5_nested_for_loop_with_connector_in_if_elseif_else.rs
new file mode 100644
index 00000000000..41ea46d4cb9
--- /dev/null
+++ b/tests/target/issue-5009/5_nested_for_loop_with_connector_in_if_elseif_else.rs
@@ -0,0 +1,15 @@
+fn main() {
+    let in_ = false;
+
+    for variable_in_x /* ... */ in 0..1 {
+        for variable_in_y /* ... */ in 0..1 {
+            if in_ {
+
+            } else if in_ {
+
+            } else {
+
+            }
+        }
+    }
+}
diff --git a/tests/target/issue-5009/6_deeply_nested_for_loop_with_connector_in_pattern.rs b/tests/target/issue-5009/6_deeply_nested_for_loop_with_connector_in_pattern.rs
new file mode 100644
index 00000000000..789e54f7e5f
--- /dev/null
+++ b/tests/target/issue-5009/6_deeply_nested_for_loop_with_connector_in_pattern.rs
@@ -0,0 +1,32 @@
+fn main() {
+    for variable_in_a /* ... */ in 0..1 {
+        for variable_in_b /* ... */ in 0..1 {
+            for variable_in_c /* ... */ in 0..1 {
+                for variable_in_d /* ... */ in 0..1 {
+                    for variable_in_e /* ... */ in 0..1 {
+                        for variable_in_f /* ... */ in 0..1 {
+                            for variable_in_g /* ... */ in 0..1 {
+                                for variable_in_h /* ... */ in 0..1 {
+                                    for variable_in_i /* ... */ in 0..1 {
+                                        for variable_in_j /* ... */ in 0..1 {
+                                            for variable_in_k /* ... */ in 0..1 {
+                                                for variable_in_l /* ... */ in 0..1 {
+                                                    for variable_in_m /* ... */ in 0..1 {
+                                                        for variable_in_n /* ... */ in 0..1 {
+                                                            for variable_in_o /* ... */ in 0..1 {
+                                                            }
+                                                        }
+                                                    }
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/tests/target/issue-5009/7_for_loop_without_connector_in_pattern.rs b/tests/target/issue-5009/7_for_loop_without_connector_in_pattern.rs
new file mode 100644
index 00000000000..cb95cecf715
--- /dev/null
+++ b/tests/target/issue-5009/7_for_loop_without_connector_in_pattern.rs
@@ -0,0 +1,4 @@
+// should not reformat
+fn main() {
+    for x /* ... */ in 0..1 {}
+}
diff --git a/tests/target/issue-5009/8_nested_for_loop_without_connector_in_pattern.rs b/tests/target/issue-5009/8_nested_for_loop_without_connector_in_pattern.rs
new file mode 100644
index 00000000000..389c524b2c1
--- /dev/null
+++ b/tests/target/issue-5009/8_nested_for_loop_without_connector_in_pattern.rs
@@ -0,0 +1,6 @@
+// should not reformat
+fn main() {
+    for x /* ... */ in 0..1 {
+        for y /* ... */ in 0..1 {}
+    }
+}