diff --git a/src/macaron/database/table_definitions.py b/src/macaron/database/table_definitions.py
index 7b173fad4..035df8f31 100644
--- a/src/macaron/database/table_definitions.py
+++ b/src/macaron/database/table_definitions.py
@@ -103,7 +103,7 @@ class PackageURLMixin:
     name: Mapped[str] = mapped_column(String(100), nullable=False, comment="Name of the package.")
 
     #: Version of the package.
-    version: Mapped[str] | None = mapped_column(String(100), nullable=True, comment="Version of the package.")
+    version: Mapped[str | None] = mapped_column(String(100), nullable=True, comment="Version of the package.")
 
     #: Extra qualifying data for a package such as the name of an OS.
     qualifiers: Mapped[str] = mapped_column(
diff --git a/src/macaron/malware_analyzer/pypi_heuristics/metadata/wheel_presence.py b/src/macaron/malware_analyzer/pypi_heuristics/metadata/wheel_presence.py
index 8610948d3..7bd2a9ddb 100644
--- a/src/macaron/malware_analyzer/pypi_heuristics/metadata/wheel_presence.py
+++ b/src/macaron/malware_analyzer/pypi_heuristics/metadata/wheel_presence.py
@@ -51,22 +51,32 @@ def analyze(self, pypi_package_json: PyPIPackageJsonAsset) -> tuple[HeuristicRes
         """
         releases = pypi_package_json.get_releases()
         if releases is None:  # no release information
-            raise HeuristicAnalyzerValueError("There is no information for any release of this package.")
+            error_msg = "There is no information for any release of this package."
+            logger.debug(error_msg)
+            raise HeuristicAnalyzerValueError(error_msg)
 
         version = pypi_package_json.component.version
         if version is None:  # check latest release version
             version = pypi_package_json.get_latest_version()
+
             if version is None:
-                raise HeuristicAnalyzerValueError("There is no latest version of this package.")
+                error_msg = "There is no latest version of this package."
+                logger.debug(error_msg)
+                raise HeuristicAnalyzerValueError(error_msg)
 
         release_files: list[JsonType] = []
         wheel_present: bool = False
 
-        for release_metadata in releases[version]:
-            if release_metadata["packagetype"] == self.WHEEL:
-                wheel_present = True
+        try:
+            for release_metadata in releases[version]:
+                if release_metadata["packagetype"] == self.WHEEL:
+                    wheel_present = True
 
-            release_files.append(release_metadata["filename"])
+                release_files.append(release_metadata["filename"])
+        except KeyError as error:
+            error_msg = f"The version {version} is not available as a release."
+            logger.debug(error_msg)
+            raise HeuristicAnalyzerValueError(error_msg) from error
 
         if wheel_present:
             return HeuristicResult.PASS, {version: release_files}