diff --git a/proptest/src/is_minimal_case.rs b/proptest/src/is_minimal_case.rs
index 65b5c9fa..39fb6def 100644
--- a/proptest/src/is_minimal_case.rs
+++ b/proptest/src/is_minimal_case.rs
@@ -49,13 +49,13 @@ pub(crate) struct MinimalCaseGuard;
 
 impl MinimalCaseGuard {
     pub(crate) fn begin_minimal_case() -> Self {
-        IS_MINIMAL_CASE.replace(true);
+        IS_MINIMAL_CASE.with(|cell| cell.replace(true));
         Self
     }
 }
 
 impl Drop for MinimalCaseGuard {
     fn drop(&mut self) {
-        IS_MINIMAL_CASE.replace(false);
+        IS_MINIMAL_CASE.with(|cell| cell.replace(false));
     }
 }
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