diff --git a/src/libslic3r/Format/3mf.cpp b/src/libslic3r/Format/3mf.cpp
index b323145d3e..3271e2c384 100644
--- a/src/libslic3r/Format/3mf.cpp
+++ b/src/libslic3r/Format/3mf.cpp
@@ -916,7 +916,12 @@ namespace Slic3r {
             }
             //FIXME Loading a "will be one day a legacy format" of configuration in a form of a G-code comment.
             // Each config line is prefixed with a semicolon (G-code comment), that is ugly.
-            config_substitutions.substitutions = config.load_from_ini_string_commented(std::move(buffer), config_substitutions.rule);
+
+            // Replacing the legacy function with load_from_ini_string_commented leads to issues when
+            // parsing 3MFs from before PrusaSlicer 2.0.0 (which can have duplicated entries in the INI.
+            // See https://github.com/prusa3d/PrusaSlicer/issues/7155. We'll revert it for now.
+            //config_substitutions.substitutions = config.load_from_ini_string_commented(std::move(buffer), config_substitutions.rule);
+            ConfigBase::load_from_gcode_string_legacy(config, buffer.data(), config_substitutions);
         }
     }
 
diff --git a/src/libslic3r/Format/AMF.cpp b/src/libslic3r/Format/AMF.cpp
index bcc5c8b4a2..235cdecb5b 100644
--- a/src/libslic3r/Format/AMF.cpp
+++ b/src/libslic3r/Format/AMF.cpp
@@ -711,7 +711,12 @@ void AMFParserContext::endElement(const char * /* name */)
         if ((m_config != nullptr) && strncmp(m_value[0].c_str(), SLIC3R_CONFIG_TYPE, strlen(SLIC3R_CONFIG_TYPE)) == 0) {
             //FIXME Loading a "will be one day a legacy format" of configuration in a form of a G-code comment.
             // Each config line is prefixed with a semicolon (G-code comment), that is ugly.
-            m_config_substitutions->substitutions = m_config->load_from_ini_string_commented(std::move(m_value[1].c_str()), m_config_substitutions->rule);
+
+            // Replacing the legacy function with load_from_ini_string_commented leads to issues when
+            // parsing 3MFs from before PrusaSlicer 2.0.0 (which can have duplicated entries in the INI.
+            // See https://github.com/prusa3d/PrusaSlicer/issues/7155. We'll revert it for now.
+            //m_config_substitutions->substitutions = m_config->load_from_ini_string_commented(std::move(m_value[1].c_str()), m_config_substitutions->rule);
+            ConfigBase::load_from_gcode_string_legacy(*m_config, std::move(m_value[1].c_str()), *m_config_substitutions);
         }
         else if (strncmp(m_value[0].c_str(), "slic3r.", 7) == 0) {
             const char *opt_key = m_value[0].c_str() + 7;