diff --git a/mitreattack/attackToExcel/stixToDf.py b/mitreattack/attackToExcel/stixToDf.py
index c6bdf6c..5d2906a 100644
--- a/mitreattack/attackToExcel/stixToDf.py
+++ b/mitreattack/attackToExcel/stixToDf.py
@@ -72,6 +72,13 @@ def get_citations(objects):
     return pd.DataFrame(citations).drop_duplicates(subset="reference", ignore_index=True)
 
 
+def _get_mapping_descriptions(dataframe):
+    """Return non-null mapping descriptions from a relationship dataframe."""
+    if "mapping description" not in dataframe.columns:
+        return []
+    return filter(lambda x: x == x, dataframe["mapping description"].tolist())
+
+
 def parseBaseStix(sdo):
     """Given an SDO, return a dict of field names:values that are common across all ATT&CK STIX types."""
     row = {}
@@ -1311,8 +1318,7 @@ def relationshipsToDf(src, relatedType=None):
             usedCitations = set()
             for dfname in dataframes:
                 df = dataframes[dfname]
-                # filter out missing descriptions which for whatever reason
-                for description in filter(lambda x: x == x, df["mapping description"].tolist()):
+                for description in _get_mapping_descriptions(df):
                     # in pandas don't equal themselves
                     [usedCitations.add(x) for x in re.findall(r"\(Citation: (.*?)\)", description)]
 
@@ -1342,7 +1348,7 @@ def _get_relationship_citations(object_dataframe, relationship_df):
             mask = relationship_df[z].values == y
             filtered = relationship_df[z].loc[mask]
             temp = set()
-            for description in filter(lambda x: x == x, filtered["mapping description"].tolist()):
+            for description in _get_mapping_descriptions(filtered):
                 [temp.add(x) for x in re.findall(r"\(Citation: (.*?)\)", description)]
             subset.append(",".join([f"(Citation: {z})" for z in temp]))
         if not new_citations:
diff --git a/tests/test_stix_to_df.py b/tests/test_stix_to_df.py
index 2655505..dcb8dc6 100644
--- a/tests/test_stix_to_df.py
+++ b/tests/test_stix_to_df.py
@@ -43,3 +43,77 @@ def test_techniques_to_df_handles_missing_tactic_definition(monkeypatch):
 
     assert len(techniques_df) == 1
     assert techniques_df.iloc[0]["tactics"] == "Defense Evasion"
+
+
+def test_techniques_to_df_handles_targets_relationship_without_description():
+    """TechniquesToDf should tolerate asset targets relationships with no description."""
+    mem_store = stix2.MemoryStore(
+        stix_data=[
+            {
+                "type": "attack-pattern",
+                "spec_version": "2.1",
+                "id": "attack-pattern--11111111-1111-4111-8111-111111111111",
+                "created": "2020-01-01T00:00:00.000Z",
+                "modified": "2020-01-01T00:00:00.000Z",
+                "name": "Test Technique",
+                "description": "Test technique",
+                "kill_chain_phases": [
+                    {
+                        "kill_chain_name": "mitre-attack",
+                        "phase_name": "inhibit-response-function",
+                    }
+                ],
+                "external_references": [
+                    {
+                        "source_name": "mitre-attack",
+                        "external_id": "T0001",
+                        "url": "https://example.com/technique",
+                    }
+                ],
+                "x_mitre_domains": ["ics-attack"],
+            },
+            {
+                "type": "x-mitre-asset",
+                "spec_version": "2.1",
+                "id": "x-mitre-asset--22222222-2222-4222-8222-222222222222",
+                "created": "2020-01-01T00:00:00.000Z",
+                "modified": "2020-01-01T00:00:00.000Z",
+                "name": "Test Asset",
+                "description": "Test asset",
+                "external_references": [
+                    {
+                        "source_name": "mitre-attack",
+                        "external_id": "A0001",
+                        "url": "https://example.com/asset",
+                    }
+                ],
+                "x_mitre_domains": ["ics-attack"],
+            },
+            {
+                "type": "relationship",
+                "spec_version": "2.1",
+                "id": "relationship--33333333-3333-4333-8333-333333333333",
+                "created": "2020-01-01T00:00:00.000Z",
+                "modified": "2020-01-01T00:00:00.000Z",
+                "relationship_type": "targets",
+                "source_ref": "attack-pattern--11111111-1111-4111-8111-111111111111",
+                "target_ref": "x-mitre-asset--22222222-2222-4222-8222-222222222222",
+                "external_references": [
+                    {
+                        "source_name": "Test Reference",
+                        "description": "Test citation",
+                        "url": "https://example.com/reference",
+                    }
+                ],
+            },
+        ]
+    )
+
+    dataframes = stixToDf.techniquesToDf(mem_store, "ics-attack")
+
+    assert "targeted assets" in dataframes
+    assert len(dataframes["targeted assets"]) == 1
+    assert dataframes["targeted assets"].iloc[0]["target name"] == "Test Asset"
+    assert dataframes["techniques"].iloc[0]["relationship citations"] == ""
+    if "citations" in dataframes:
+        assert dataframes["citations"].empty