diff --git a/rsrcfork/compress/dcmp0.py b/rsrcfork/compress/dcmp0.py
index bb48c2b..ca560be 100644
--- a/rsrcfork/compress/dcmp0.py
+++ b/rsrcfork/compress/dcmp0.py
@@ -40,7 +40,7 @@ def decompress(header_info: common.CompressedHeaderInfo, data: bytes, *, debug:
 	"""Decompress compressed data in the format used by 'dcmp' (0)."""
 	
 	if not isinstance(header_info, common.CompressedApplicationHeaderInfo):
-		raise common.DecompressError(f"Incorrect header type: {type(header_info.__qualname__)}")
+		raise common.DecompressError(f"Incorrect header type: {type(header_info).__qualname__}")
 	
 	prev_literals = []
 	decompressed = b""
diff --git a/rsrcfork/compress/dcmp1.py b/rsrcfork/compress/dcmp1.py
index a97492c..2343528 100644
--- a/rsrcfork/compress/dcmp1.py
+++ b/rsrcfork/compress/dcmp1.py
@@ -23,7 +23,7 @@ def decompress(header_info: common.CompressedHeaderInfo, data: bytes, *, debug:
 	"""Decompress compressed data in the format used by 'dcmp' (1)."""
 	
 	if not isinstance(header_info, common.CompressedApplicationHeaderInfo):
-		raise common.DecompressError(f"Incorrect header type: {type(header_info.__qualname__)}")
+		raise common.DecompressError(f"Incorrect header type: {type(header_info).__qualname__}")
 	
 	prev_literals = []
 	decompressed = b""
diff --git a/rsrcfork/compress/dcmp2.py b/rsrcfork/compress/dcmp2.py
index 07be70a..846ff36 100644
--- a/rsrcfork/compress/dcmp2.py
+++ b/rsrcfork/compress/dcmp2.py
@@ -135,7 +135,7 @@ def decompress(header_info: common.CompressedHeaderInfo, data: bytes, *, debug:
 	"""Decompress compressed data in the format used by 'dcmp' (2)."""
 	
 	if not isinstance(header_info, common.CompressedSystemHeaderInfo):
-		raise common.DecompressError(f"Incorrect header type: {type(header_info.__qualname__)}")
+		raise common.DecompressError(f"Incorrect header type: {type(header_info).__qualname__}")
 	
 	unknown, table_count_m1, flags_raw = STRUCT_PARAMETERS.unpack(header_info.parameters)