diff --git a/etoolbox.sty b/etoolbox.sty
index c4c5b37..880c555 100644
--- a/etoolbox.sty
+++ b/etoolbox.sty
@@ -942,16 +942,16 @@
     {\edef#1{\expandonce#1\unexpanded{#2}}}}
 \newrobustcmd{\eappto}[2]{%
   \ifundef{#1}
-    {\edef#1{#2}}
-    {\edef#1{\expandonce#1#2}}}
+    {\edef#1{\expandonce{\expanded{#2}}}}
+    {\edef#1{\expandonce#1\expandonce{\expanded{#2}}}}}
 \newrobustcmd{\gappto}[2]{%
   \ifundef{#1}
     {\xdef#1{\unexpanded{#2}}}
     {\xdef#1{\expandonce#1\unexpanded{#2}}}}
 \newrobustcmd{\xappto}[2]{%
   \ifundef{#1}
-    {\xdef#1{#2}}
-    {\xdef#1{\expandonce#1#2}}}
+    {\xdef#1{\expandonce{\expanded{#2}}}}
+    {\xdef#1{\expandonce#1\expandonce{\expanded{#2}}}}}
 
 \newrobustcmd*{\protected@eappto}{\etb@protected\eappto}
 \newrobustcmd*{\protected@xappto}{\etb@protected\xappto}
@@ -964,16 +964,16 @@
     {\edef#1{\unexpanded{#2}\expandonce#1}}}
 \newrobustcmd{\epreto}[2]{%
   \ifundef{#1}
-    {\edef#1{#2}}
-    {\edef#1{#2\expandonce#1}}}
+    {\edef#1{\expandonce{\expanded{#2}}}}
+    {\edef#1{\expandonce{\expanded{#2}}\expandonce#1}}}
 \newrobustcmd{\gpreto}[2]{%
   \ifundef{#1}
     {\xdef#1{\unexpanded{#2}}}
     {\xdef#1{\unexpanded{#2}\expandonce#1}}}
 \newrobustcmd{\xpreto}[2]{%
   \ifundef{#1}
-    {\xdef#1{#2}}
-    {\xdef#1{#2\expandonce#1}}}
+    {\xdef#1{\expandonce{\expanded{#2}}}}
+    {\xdef#1{\expandonce{\expanded{#2}}\expandonce#1}}}
 
 \newrobustcmd*{\protected@epreto}{\etb@protected\epreto}
 \newrobustcmd*{\protected@xpreto}{\etb@protected\xpreto}
diff --git a/testfiles/etoolbox-eappto.lvt b/testfiles/etoolbox-eappto.lvt
new file mode 100644
index 0000000..8da4a0b
--- /dev/null
+++ b/testfiles/etoolbox-eappto.lvt
@@ -0,0 +1,64 @@
+\input{regression-test}
+\RequirePackage{etoolbox}
+
+\START
+
+\def\mmeaning#1{\string#1\space= {\meaning#1}}
+\def\inputa{a}
+\def\inputb{b}
+\def\inputc{c}
+\def\inputd{d}
+\def\inpute{e}
+\def\inputee{\inpute}
+\toks0={\unexpandingmacro}
+
+\TEST{\eappto regression test}{
+    \TYPE{\mmeaning\test}
+    \eappto\test{\inputa}
+    \TYPE{\mmeaning\test}
+    \eappto\test{\inputb\inputc}
+    \TYPE{\mmeaning\test}
+    \eappto\test{(\noexpand\inputd = \inputd)}
+    \TYPE{\mmeaning\test}
+    \eappto\test{(\expandonce\inputee = \inputee)}
+    \TYPE{\mmeaning\test}
+    \eappto\test{\the\toks0}
+    \TYPE{\mmeaning\test}
+}
+
+\TEST{\epreto regression test}{
+    \let\test\undefined
+    \TYPE{\mmeaning\test}
+    \epreto\test{\inputa}
+    \TYPE{\mmeaning\test}
+    \epreto\test{\inputb\inputc}
+    \TYPE{\mmeaning\test}
+    \epreto\test{(\noexpand\inputd = \inputd)}
+    \TYPE{\mmeaning\test}
+    \epreto\test{(\expandonce\inputee = \inputee)}
+    \TYPE{\mmeaning\test}
+    \epreto\test{\the\toks0}
+    \TYPE{\mmeaning\test}
+}
+
+\TEST{\eappto & \epreto with hash symbols}{
+    \def\two{four}
+    \def\four{eight}
+    \let\test\undefined
+    \eappto\test{
+        \unexpanded{\edef\lazyedef}{
+            only \unexpanded{\two} hash symbols (##) needed to escape
+            instead of \unexpanded{\four}}
+    }
+    \epreto\test{
+        \unexpanded{\def\lazydef#1#2}{do something with #1 and #2}
+    }
+    \def\two{two}
+    \def\four{four}
+    \test
+    \TYPE{\mmeaning\lazyedef}
+    \TYPE{\mmeaning\lazydef}
+    \TYPE{\string\lazydef{arg1}{arg2} = \lazydef{arg1}{arg2}}
+}
+
+\END
diff --git a/testfiles/etoolbox-eappto.tlg b/testfiles/etoolbox-eappto.tlg
new file mode 100644
index 0000000..c2eced0
--- /dev/null
+++ b/testfiles/etoolbox-eappto.tlg
@@ -0,0 +1,29 @@
+This is a generated file for the l3build validation system.
+Don't change this file in any respect.
+============================================================
+TEST 1: \eappto regression test
+============================================================
+\test = {undefined}
+\test = {macro:->a}
+\test = {macro:->abc}
+\test = {macro:->abc(\inputd = d)}
+\test = {macro:->abc(\inputd = d)(\inpute = e)}
+\test = {macro:->abc(\inputd = d)(\inpute = e)\unexpandingmacro }
+============================================================
+============================================================
+TEST 2: \epreto regression test
+============================================================
+\test = {undefined}
+\test = {macro:->a}
+\test = {macro:->bca}
+\test = {macro:->(\inputd = d)bca}
+\test = {macro:->(\inpute = e)(\inputd = d)bca}
+\test = {macro:->\unexpandingmacro (\inpute = e)(\inputd = d)bca}
+============================================================
+============================================================
+TEST 3: \eappto & \epreto with hash symbols
+============================================================
+\lazyedef = {macro:-> only two hash symbols (##) needed to escape instead of four}
+\lazydef = {macro:#1#2->do something with #1 and #2}
+\lazydef{arg1}{arg2} = do something with arg1 and arg2
+============================================================