diff --git a/src/Text/Pandoc/Writers/LaTeX.hs b/src/Text/Pandoc/Writers/LaTeX.hs
index 70744bde3..18138bf4c 100644
--- a/src/Text/Pandoc/Writers/LaTeX.hs
+++ b/src/Text/Pandoc/Writers/LaTeX.hs
@@ -1124,7 +1124,12 @@ inlineToLaTeX (Image attr _ (source, _)) = do
                          Just dim         ->
                            [d <> text (show dim)]
                          Nothing          ->
-                           []
+                           case dir of
+                                Width | isJust (dimension Height attr) ->
+                                  [d <> "\\textwidth"]
+                                Height | isJust (dimension Width attr) ->
+                                  [d <> "\\textheight"]
+                                _ -> []
       dimList = showDim Width ++ showDim Height
       dims = if null dimList
                 then empty
diff --git a/test/command/3450.md b/test/command/3450.md
index 8759aa0c1..5b35e1d9e 100644
--- a/test/command/3450.md
+++ b/test/command/3450.md
@@ -8,5 +8,5 @@
 % pandoc -fmarkdown-implicit_figures -t latex
 ![image](lalune.jpg){height=2em}
 ^D
-\includegraphics[height=2em]{lalune.jpg}
+\includegraphics[width=\textwidth,height=2em]{lalune.jpg}
 ```