diff --git a/ext/zstdruby/zstdruby.c b/ext/zstdruby/zstdruby.c
index 1649fe5..54608ad 100644
--- a/ext/zstdruby/zstdruby.c
+++ b/ext/zstdruby/zstdruby.c
@@ -51,6 +51,7 @@ static VALUE decode_one_frame(ZSTD_DCtx* dctx, const unsigned char* src, size_t
 
   for (;;) {
     ZSTD_outBuffer o = (ZSTD_outBuffer){ buf, cap, 0 };
+    size_t const in_pos_before = in.pos;
     size_t ret = ZSTD_decompressStream(dctx, &o, &in);
     if (ZSTD_isError(ret)) {
       xfree(buf);
@@ -62,6 +63,13 @@ static VALUE decode_one_frame(ZSTD_DCtx* dctx, const unsigned char* src, size_t
     if (ret == 0) {
       break;
     }
+    if (o.pos == 0 && in.pos == in_pos_before) {
+      /* No progress: the frame is truncated/incomplete. Without this guard the
+         loop would spin forever calling ZSTD_decompressStream on exhausted
+         input (see decompress of a header-only frame). */
+      xfree(buf);
+      rb_raise(rb_eRuntimeError, "ZSTD_decompressStream failed: truncated or incomplete frame");
+    }
   }
   xfree(buf);
   return out;
diff --git a/spec/zstd-ruby_spec.rb b/spec/zstd-ruby_spec.rb
index ddfae47..c302217 100644
--- a/spec/zstd-ruby_spec.rb
+++ b/spec/zstd-ruby_spec.rb
@@ -103,6 +103,18 @@ def to_str
       expect { Zstd.decompress(Object.new) }.to raise_error(TypeError)
     end
 
+    it 'should raise (not hang) on a truncated frame' do
+      full = Zstd.compress('a' * 2000)
+      [
+        "\x28\xB5\x2F\xFD".b, # bare zstd magic, no body
+        full.byteslice(0, 5),
+        full.byteslice(0, 6),
+        full.byteslice(0, full.bytesize / 2),
+      ].each do |truncated|
+        expect { Zstd.decompress(truncated) }.to raise_error(RuntimeError)
+      end
+    end
+
     class DummyForDecompress
       def to_str
         Zstd.compress('abc')