diff --git a/CHANGELOG.md b/CHANGELOG.md
index 45163b8c0..cbae22d49 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ Bug fixes
 
 * (Fuzzing) An integer-overflow bug from an inclusive range in the bits iterator is fixed.
 * (Fuzzing) An integer-underflow bug from an inclusive range is fixed.
+* Copy strings if the strings interner is busy instead of panicing.
 
 New features
 ------------
diff --git a/src/engine.rs b/src/engine.rs
index 771bff9f5..1937229dc 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -344,7 +344,10 @@ impl Engine {
         string: impl AsRef<str> + Into<ImmutableString>,
     ) -> ImmutableString {
         match self.interned_strings {
-            Some(ref interner) => locked_write(interner).unwrap().get(string),
+            Some(ref interner) => match locked_write(interner) {
+                Some(mut cache) => cache.get(string),
+                None => string.into(),
+            },
             None => string.into(),
         }
     }
@@ -357,11 +360,12 @@ impl Engine {
         text: impl AsRef<str> + Into<ImmutableString>,
     ) -> ImmutableString {
         match self.interned_strings {
-            Some(ref interner) => locked_write(interner).unwrap().get_with_mapper(
-                b'g',
-                |s| make_getter(s.as_ref()).into(),
-                text,
-            ),
+            Some(ref interner) => match locked_write(interner) {
+                Some(mut cache) => {
+                    cache.get_with_mapper(b'g', |s| make_getter(s.as_ref()).into(), text)
+                }
+                None => make_getter(text.as_ref()).into(),
+            },
             None => make_getter(text.as_ref()).into(),
         }
     }
@@ -375,11 +379,12 @@ impl Engine {
         text: impl AsRef<str> + Into<ImmutableString>,
     ) -> ImmutableString {
         match self.interned_strings {
-            Some(ref interner) => locked_write(interner).unwrap().get_with_mapper(
-                b's',
-                |s| make_setter(s.as_ref()).into(),
-                text,
-            ),
+            Some(ref interner) => match locked_write(interner) {
+                Some(mut cache) => {
+                    cache.get_with_mapper(b's', |s| make_setter(s.as_ref()).into(), text)
+                }
+                None => make_setter(text.as_ref()).into(),
+            },
             None => make_setter(text.as_ref()).into(),
         }
     }