diff --git a/rendercv/themes/classic/Preamble.j2.tex b/rendercv/themes/classic/Preamble.j2.tex
index 40f2acc..ef293bb 100644
--- a/rendercv/themes/classic/Preamble.j2.tex
+++ b/rendercv/themes/classic/Preamble.j2.tex
@@ -32,12 +32,13 @@
 \usepackage{paracol} % for two and three column entries
 \usepackage{ifthen} % for conditional statements
 \usepackage{needspace} % for avoiding page brake right after the section title
+\usepackage{iftex} % check if engine is pdflatex, xetex or luatex
 
 % Theme specific:
 \usepackage[default, type1]{sourcesanspro} % for using source sans 3 font
 
 % Ensure that generate pdf is machine readable/ATS parsable:
-\ifpdf
+\ifPDFTeX
     \input{glyphtounicode}
     \pdfgentounicode=1
 \fi
diff --git a/rendercv/themes/engineeringresumes/Preamble.j2.tex b/rendercv/themes/engineeringresumes/Preamble.j2.tex
index 86091c0..77576a5 100644
--- a/rendercv/themes/engineeringresumes/Preamble.j2.tex
+++ b/rendercv/themes/engineeringresumes/Preamble.j2.tex
@@ -32,12 +32,13 @@
 \usepackage{paracol} % for two and three column entries
 \usepackage{ifthen} % for conditional statements
 \usepackage{needspace} % for avoiding page brake right after the section title
+\usepackage{iftex} % check if engine is pdflatex, xetex or luatex
 
 % Theme specific:
 \usepackage{charter} % for using charter font
 
 % Ensure that generate pdf is machine readable/ATS parsable:
-\ifpdf
+\ifPDFTeX
     \input{glyphtounicode}
     \pdfgentounicode=1
 \fi
diff --git a/rendercv/themes/sb2nov/Preamble.j2.tex b/rendercv/themes/sb2nov/Preamble.j2.tex
index d496a77..c7f5b72 100644
--- a/rendercv/themes/sb2nov/Preamble.j2.tex
+++ b/rendercv/themes/sb2nov/Preamble.j2.tex
@@ -32,9 +32,10 @@
 \usepackage{paracol} % for two and three column entries
 \usepackage{ifthen} % for conditional statements
 \usepackage{needspace} % for avoiding page brake right after the section title
+\usepackage{iftex} % check if engine is pdflatex, xetex or luatex
 
 % Ensure that generate pdf is machine readable/ATS parsable:
-\ifpdf
+\ifPDFTeX
     \input{glyphtounicode}
     \pdfgentounicode=1
 \fi