2 files changed, 4 insertions, 0 deletions
diff --git a/src/main/java/org/zwobble/mammoth/internal/docx/ReadResult.java b/src/main/java/org/zwobble/mammoth/internal/docx/ReadResult.java
index 95b886f..65cd3b0 100644
--- a/src/main/java/org/zwobble/mammoth/internal/docx/ReadResult.java
+++ b/src/main/java/org/zwobble/mammoth/internal/docx/ReadResult.java
@@ -12,11 +12,13 @@ import static org.zwobble.mammoth.internal.util.MammothIterables.lazyConcat;
 import static org.zwobble.mammoth.internal.util.MammothIterables.lazyFlatMap;
 import static org.zwobble.mammoth.internal.util.MammothLists.eagerFlatMap;
 import static org.zwobble.mammoth.internal.util.MammothLists.list;
+import static org.zwobble.mammoth.internal.util.MammothLists.toList;
 
 public class ReadResult {
     public static final ReadResult EMPTY_SUCCESS = success(list());
 
     public static ReadResult concat(Iterable<ReadResult> results) {
+        results = toList(results);
         return new ReadResult(
             eagerFlatMap(results, result -> result.elements),
             eagerFlatMap(results, result -> result.extra),
diff --git a/src/main/java/org/zwobble/mammoth/internal/results/InternalResult.java b/src/main/java/org/zwobble/mammoth/internal/results/InternalResult.java
index 35c195d..b4c3791 100644
--- a/src/main/java/org/zwobble/mammoth/internal/results/InternalResult.java
+++ b/src/main/java/org/zwobble/mammoth/internal/results/InternalResult.java
@@ -14,9 +14,11 @@ import static org.zwobble.mammoth.internal.util.MammothIterables.lazyConcat;
 import static org.zwobble.mammoth.internal.util.MammothIterables.lazyFlatMap;
 import static org.zwobble.mammoth.internal.util.MammothLists.eagerMap;
 import static org.zwobble.mammoth.internal.util.MammothLists.list;
+import static org.zwobble.mammoth.internal.util.MammothLists.toList;
 
 public class InternalResult<T> {
     public static <T> InternalResult<List<T>> concat(Iterable<InternalResult<T>> results) {
+        results = toList(results);
         return new InternalResult<>(
             eagerMap(results, result -> result.value),
             lazyFlatMap(results, result -> result.warnings));