diff --git a/clippy_lints/src/manual_assert.rs b/clippy_lints/src/manual_assert.rs
index 4f6a2cf017c..76edbe8b755 100644
--- a/clippy_lints/src/manual_assert.rs
+++ b/clippy_lints/src/manual_assert.rs
@@ -1,7 +1,7 @@
 use crate::rustc_lint::LintContext;
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::macros::root_macro_call;
-use clippy_utils::{is_else_clause, peel_blocks_with_stmt, span_extract_comment, sugg};
+use clippy_utils::{is_else_clause, is_parent_stmt, peel_blocks_with_stmt, span_extract_comment, sugg};
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind, UnOp};
 use rustc_lint::{LateContext, LateLintPass};
@@ -63,7 +63,8 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
                 _ => (cond, "!"),
             };
             let cond_sugg = sugg::Sugg::hir_with_applicability(cx, cond, "..", &mut applicability).maybe_par();
-            let sugg = format!("assert!({not}{cond_sugg}, {format_args_snip});");
+            let semicolon = if is_parent_stmt(cx, expr.hir_id) { ";" } else { "" };
+            let sugg = format!("assert!({not}{cond_sugg}, {format_args_snip}){semicolon}");
             // we show to the user the suggestion without the comments, but when applying the fix, include the
             // comments in the block
             span_lint_and_then(
diff --git a/tests/ui/manual_assert.edition2018.fixed b/tests/ui/manual_assert.edition2018.fixed
index 75beedfa450..75835780801 100644
--- a/tests/ui/manual_assert.edition2018.fixed
+++ b/tests/ui/manual_assert.edition2018.fixed
@@ -66,3 +66,11 @@ fn issue7730(a: u8) {
 // comment after `panic!`
 assert!(!(a > 2), "panic with comment");
 }
+
+fn issue12505() {
+    struct Foo<T, const N: usize>(T);
+
+    impl<T, const N: usize> Foo<T, N> {
+        const BAR: () = assert!(!(N == 0), );
+    }
+}
diff --git a/tests/ui/manual_assert.edition2018.stderr b/tests/ui/manual_assert.edition2018.stderr
index 57015933d40..1eebe1bfe17 100644
--- a/tests/ui/manual_assert.edition2018.stderr
+++ b/tests/ui/manual_assert.edition2018.stderr
@@ -82,5 +82,14 @@ help: try instead
 LL |     assert!(!(a > 2), "panic with comment");
    |
 
-error: aborting due to 9 previous errors
+error: only a `panic!` in `if`-then statement
+  --> tests/ui/manual_assert.rs:91:25
+   |
+LL |           const BAR: () = if N == 0 {
+   |  _________________________^
+LL | |             panic!()
+LL | |         };
+   | |_________^ help: try instead: `assert!(!(N == 0), )`
+
+error: aborting due to 10 previous errors
 
diff --git a/tests/ui/manual_assert.edition2021.fixed b/tests/ui/manual_assert.edition2021.fixed
index 75beedfa450..75835780801 100644
--- a/tests/ui/manual_assert.edition2021.fixed
+++ b/tests/ui/manual_assert.edition2021.fixed
@@ -66,3 +66,11 @@ fn issue7730(a: u8) {
 // comment after `panic!`
 assert!(!(a > 2), "panic with comment");
 }
+
+fn issue12505() {
+    struct Foo<T, const N: usize>(T);
+
+    impl<T, const N: usize> Foo<T, N> {
+        const BAR: () = assert!(!(N == 0), );
+    }
+}
diff --git a/tests/ui/manual_assert.edition2021.stderr b/tests/ui/manual_assert.edition2021.stderr
index 57015933d40..1eebe1bfe17 100644
--- a/tests/ui/manual_assert.edition2021.stderr
+++ b/tests/ui/manual_assert.edition2021.stderr
@@ -82,5 +82,14 @@ help: try instead
 LL |     assert!(!(a > 2), "panic with comment");
    |
 
-error: aborting due to 9 previous errors
+error: only a `panic!` in `if`-then statement
+  --> tests/ui/manual_assert.rs:91:25
+   |
+LL |           const BAR: () = if N == 0 {
+   |  _________________________^
+LL | |             panic!()
+LL | |         };
+   | |_________^ help: try instead: `assert!(!(N == 0), )`
+
+error: aborting due to 10 previous errors
 
diff --git a/tests/ui/manual_assert.rs b/tests/ui/manual_assert.rs
index 5979496ca83..363bafdf05d 100644
--- a/tests/ui/manual_assert.rs
+++ b/tests/ui/manual_assert.rs
@@ -83,3 +83,13 @@ fn issue7730(a: u8) {
         panic!("panic with comment") // comment after `panic!`
     }
 }
+
+fn issue12505() {
+    struct Foo<T, const N: usize>(T);
+
+    impl<T, const N: usize> Foo<T, N> {
+        const BAR: () = if N == 0 {
+            panic!()
+        };
+    }
+}