diff --git a/doc/generic/pgf/CHANGELOG.md b/doc/generic/pgf/CHANGELOG.md
index 3f5b2e53c..b12f67ccf 100644
--- a/doc/generic/pgf/CHANGELOG.md
+++ b/doc/generic/pgf/CHANGELOG.md
@@ -22,6 +22,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Treat varargs for `min()` and `max()` in `luamath` pgf library pgf-tikz/pgfplots#492 #1359
 - Fixed support for the `\tikz` command in the `dvisvgm4ht` driver for TeX4ht
 - Wrong key name in unknown decoration option error #1082
+- `gnuplot` was always run when the function contained leading or trailing spaces #1397
 
 ### Changed
 
diff --git a/tex/generic/pgf/frontendlayer/tikz/tikz.code.tex b/tex/generic/pgf/frontendlayer/tikz/tikz.code.tex
index d9b1743b9..8868d5d7f 100644
--- a/tex/generic/pgf/frontendlayer/tikz/tikz.code.tex
+++ b/tex/generic/pgf/frontendlayer/tikz/tikz.code.tex
@@ -3365,7 +3365,8 @@
 \def\tikz@plot@function unction#1{%
   \def\tikz@plot@filename{\tikz@plot@prefix\tikz@plot@id}%
   \iftikz@plot@raw@gnuplot%
-    \def\tikz@plot@data{\pgfplotgnuplot[\tikz@plot@filename]{#1}}%
+    \def\tikz@plot@data{%
+      \pgfplotgnuplot[\tikz@plot@filename]{\pgfutil@trimspaces@e{#1}}}%
   \else%
     \iftikz@plot@parametric%
       \def\tikz@plot@data{\pgfplotgnuplot[\tikz@plot@filename]{%
@@ -3374,13 +3375,13 @@
           plot [t=\tikz@plot@domain]
           [\tikz@plot@xrange]
           [\tikz@plot@range]
-          #1}}%
+          \pgfutil@trimspaces@e{#1}}}%
     \else%
       \def\tikz@plot@data{\pgfplotgnuplot[\tikz@plot@filename]{%
           set samples \tikz@plot@samples;
           plot [x=\tikz@plot@domain]
           \ifx\tikz@plot@range\pgfutil@empty\else[\tikz@plot@range]\fi
-          #1}}%
+          \pgfutil@trimspaces@e{#1}}}%
     \fi%
   \fi%
   \tikz@@@plot%
diff --git a/tex/generic/pgf/modules/pgfmoduleplot.code.tex b/tex/generic/pgf/modules/pgfmoduleplot.code.tex
index 5135d4eec..4dbaa14f0 100644
--- a/tex/generic/pgf/modules/pgfmoduleplot.code.tex
+++ b/tex/generic/pgf/modules/pgfmoduleplot.code.tex
@@ -481,6 +481,8 @@
   \pgfutilpreparefilename{#1.table}%
   \let\pgf@plottablefile=\pgfretval
   \let\pgf@plottablefile@quoted=\pgfretvalquoted
+  \begingroup
+  \endlinechar=-1 % suppress white space at end
   % Check, whether it is up-to-date
   \openin\pgfutil@inputcheck=\pgf@plotgnuplotfile\relax
   \ifeof\pgfutil@inputcheck%
@@ -488,7 +490,7 @@
     \pgfutil@read\pgfutil@inputcheck to\pgf@temp% ignored
     \pgfutil@read\pgfutil@inputcheck to\pgf@plot@line%
     \closein\pgfutil@inputcheck
-    \edef\pgf@plot@code{#2\space}%
+    \edef\pgf@plot@code{\pgfutil@trimspaces@e{#2}}%
     \ifx\pgf@plot@code\pgf@plot@line%
       \openin\pgfutil@inputcheck=\pgfretval\relax
       \ifeof\pgfutil@inputcheck%
@@ -501,11 +503,12 @@
   \ifpgf@resample@plot%
     \immediate\openout\pgf@plotwrite=\pgf@plotgnuplotfile\relax
     \immediate\pgfutil@write\pgf@plotwrite{\pgf@gnuplot@head}%
-    \immediate\pgfutil@write\pgf@plotwrite{#2}%
+    \immediate\pgfutil@write\pgf@plotwrite{\pgf@plot@code}%
     \immediate\closeout\pgf@plotwrite%
     \pgfutil@shellescape{%
       \pgfkeysvalueof{/pgf/plot/gnuplot call} \pgf@plotgnuplotfile}%
   \fi%
+  \endgroup
 %  \let\pgf@savedparsexyline=\pgf@parsexyline%
 %  \let\pgf@parsexyline=\pgf@parsegnuplotxyline%
   \pgfplotxyfile{\pgf@plottablefile}%
diff --git a/tex/generic/pgf/utilities/pgfutil-common.tex b/tex/generic/pgf/utilities/pgfutil-common.tex
index 1bf2e247a..66c6fd015 100644
--- a/tex/generic/pgf/utilities/pgfutil-common.tex
+++ b/tex/generic/pgf/utilities/pgfutil-common.tex
@@ -49,6 +49,10 @@
 \def\pgfutil@trimspaces@@#1Q#2{#1}
 \catcode`\Q=11
 
+\def\pgfutil@trimspaces@e#1{%
+  \expandafter\pgfutil@trimspaces\expandafter{\pgfutil@expanded{#1}}%
+}
+
 % \pgfutil@ifx{<token 1>}{<token 2>}{<true code>}{<false code>}
 %
 % This macro is expandable.