diff --git a/adb/types.cpp b/adb/types.cpp
index 26b77ab..9cdf32b 100644
--- a/adb/types.cpp
+++ b/adb/types.cpp
@@ -51,7 +51,7 @@
     auto dropped = 0u;
     while (dropped < len) {
         const auto next = chain_[start_index_].size() - begin_offset_;
-        if (dropped + next < len) {
+        if (dropped + next <= len) {
             pop_front_block();
             dropped += next;
         } else {
diff --git a/adb/types.h b/adb/types.h
index deca7ea..620aa8e 100644
--- a/adb/types.h
+++ b/adb/types.h
@@ -155,7 +155,7 @@
             return nullptr;
         }
 
-        return chain_.front().data() + begin_offset_;
+        return chain_[start_index_].data() + begin_offset_;
     }
 
     size_type front_size() const {
@@ -163,7 +163,7 @@
             return 0;
         }
 
-        return chain_.front().size() - begin_offset_;
+        return chain_[start_index_].size() - begin_offset_;
     }
 
     size_type size() const { return chain_length_ - begin_offset_; }
diff --git a/adb/types_test.cpp b/adb/types_test.cpp
index 2c99f95..41fa1db 100644
--- a/adb/types_test.cpp
+++ b/adb/types_test.cpp
@@ -117,3 +117,20 @@
     ASSERT_EQ(1ULL, bc.size());
     ASSERT_EQ(create_block("x"), bc.coalesce());
 }
+
+TEST(IOVector, drop_front) {
+    IOVector vec;
+
+    vec.append(create_block('x', 2));
+    vec.append(create_block('y', 1000));
+    ASSERT_EQ(2U, vec.front_size());
+    ASSERT_EQ(1002U, vec.size());
+
+    vec.drop_front(1);
+    ASSERT_EQ(1U, vec.front_size());
+    ASSERT_EQ(1001U, vec.size());
+
+    vec.drop_front(1);
+    ASSERT_EQ(1000U, vec.front_size());
+    ASSERT_EQ(1000U, vec.size());
+}