diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4d2f5c2..0be11f9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - Fix panic in `tlsf::Heap::used`.
+- Fix panic in `tlsf::Heap::free` in case the value returned from `insert_free_block_ptr`
+  does not conver the full memory range passed in.
 
 ## [v0.7.0] - 2026-01-03
 
diff --git a/src/tlsf.rs b/src/tlsf.rs
index 7155aaa..57f91a0 100644
--- a/src/tlsf.rs
+++ b/src/tlsf.rs
@@ -70,18 +70,26 @@ impl Heap {
     /// This function will panic if either of the following are true:
     ///
     /// - this function is called more than ONCE.
-    /// - `size == 0`.
+    /// - `size`, after aligning start and end to `rlsf::GRANULARITY`, is smaller than `rlsf::GRANULARITY * 2`.
     pub unsafe fn init(&self, start_addr: usize, size: usize) {
         assert!(size > 0);
         critical_section::with(|cs| {
             let mut heap = self.heap.borrow_ref_mut(cs);
             assert!(!heap.initialized);
-            heap.initialized = true;
             let block: NonNull<[u8]> =
                 NonNull::slice_from_raw_parts(NonNull::new_unchecked(start_addr as *mut u8), size);
-            heap.tlsf.insert_free_block_ptr(block);
-            heap.raw_block = Some(block);
-            heap.raw_block_size = size;
+            if let Some(actual_size) = heap.tlsf.insert_free_block_ptr(block) {
+                let block: NonNull<[u8]> = NonNull::slice_from_raw_parts(
+                    NonNull::new_unchecked(start_addr as *mut u8),
+                    actual_size.get(),
+                );
+                heap.initialized = true;
+                heap.raw_block = Some(block);
+                heap.raw_block_size = size;
+            }
+            if !heap.initialized {
+                panic!("Allocation too small for heap");
+            }
         });
     }